Search

When conducting experiments on the electric explosion of titanium foil in water, a “strange” radiation was detected, leaving dotted traces on the film. The velocity of the carriers of this radiation was estimated as 20–40 m/s, and their energy, estimated by the Coulomb drag mechanism, turned out to be equal to 700 MeV. Subsequently, it was found that similar traces are formed at various types of high-current arc discharges, both of artificial and natural origin. Many solutions have been proposed to explain the nature of “strange” radiation, but none of them describes the details of the process of formation of dotted traces. We believe that these traces on the film could appear due to the action of charged micron-sized clusters. The possibility of the existence of clusters in the form of a nucleus from a certain number of similarly charged ions enclosed in a spherical shell of water molecules is shown. The force of the Coulomb repulsion of ions is compensated by the compression force of the shell polarized by the inhomogeneous electric field created by the nuclear charge. As the cluster approaches the surface of the film, a cluster with a small charge separates from it. It is accelerated in the electric field of a “large” cluster to energy of about 1 GeV. Having received a recoil momentum, a large cluster moves away from the film, braking in an inhomogeneous electric field, and then “falls” onto it again, and the process is repeated.

The paper presents the results of comparative studies on the modifying ability of La, Sc (REM group), and Sr (AEM group) in the processing of a GK-AlSi10Mgwa alloy (Al–Si–Mg system). The elements were introduced into the melt in the form of AlLa12, AlSc2, and AlSr10 master alloys in the same amount (0.25 wt.%). The effects of the added elements on the microstructure, mechanical properties, and electrical conductivity in the cast state were evaluated. Structural homogeneity was evaluated along the height of the plate samples according to recorded electrical conductivity values. Varying degrees of modification were used to enhance the mechanical properties and electrical conductivity of the GK-AlSi10Mgwa alloy. While, upon modification with Sr additives, the maximum increase in ultimate strength (by 60–66%) was noted, the HB hardness and the relative elongation of the alloy increased to a lesser extent in comparison with modification by La and Sc. Modifiers of the REM group (La and Sc) altered the morphology of the main phases in different ways. In La-modified samples, the morphology of eutectic silicon crystals was changed from lamellar to fibrous. Modification by Sc additives caused similar changes in the morphology of eutectic silicon with partial modification of α-Al dendrites. In terms of modifying α-Al dendrites and eutectic silicon crystals, strontium – an alkaline-earth metal – had the greatest effect. Such modification leads to changes in the alloy structure, eventually resulting in increased electrical conductivity. Although the maximum increase in electrical conductivity was brought about by Sr-modification of the alloy samples, the fact that this change is not significant indicates an increase in the homogeneity of the microstructure.

The article proposes an invention to diagnose a damaged insulator under the operating voltage of the power line (VLEP), using leakage current control. There is made a prototype, experiments are carried out. The leakage current removed from the shunt design is converted to a digital signal for processing, transmission and further processing on the substation control room. The controlled leakage current corresponds to the magnitude of the insulation resistance of the insulator

The electric field effect in electron spin resonance spectra of Fe3+ and Mn4+ impurity ions in thin oriented single-crystal plates of strontium titanate has been studied; the crystal structure of these samples at T > 105 K is tetragonal (i.e., differs from both cubic and antiferrodistortive tetragonal structure that is inherent in SrTiO3 at T < 105 K). It is shown that the electric field effects for the investigated centers are quadratic with respect to the applied field and have identical signs and orders of magnitude, thus indicating a nonpolar character of the observed high-temperature tetragonal state. An analysis of the dependences of the axiality value on the applied field indicates that the electric field effect is not related to electrostriction and caused by modification of the wave function of the ground state of impurity centers.

В статье рассматривается исследование, посвященное разработке камеры нагрева установки для исследования зависимостей характеристик частичных разрядов от температуры. Разработаны требования безопасной эксплуатации установки при условии размещения внутри камеры нагрева образца кабеля под напряжением. Построены геометрические модели вертикального и горизонтального исполнения камеры нагрева. В построенных моделях определены картины распределения температуры внутри камеры нагрева. Наибольший интерес представляет тепволое поле на поверхности кабеля, так как оно существенно влияет на характеристики частичных разрядов в изоляции кабелей. Полученные результаты показали превышение допустимой разницы в температуре поверхности кабеля. В последующей работе будут проведены мероприятия для снижения неравномерности теплового поля путем корректировки коэффициентов теплопередачи или изменения геометрии модели установки.

The paper investigates the existing mathematical models of insulation destruction. It has been determined that most of the models for assessing the residual life of insulation are based on models of thermal and thermo-oxidative destruction of insulation materials. Currently, solid dielectrics are gaining popularity, including crosslinked polyethylene, PVC, ethylene-propylene rubber, and others. In such dielectrics, it is possible to estimate the residual life in the short term. This possibility and necessity is due to the possibility of growth of tree defects under the influence of partial discharges. The article describes the proposed mathematical model for assessing the residual resource of insulation by modeling the growth of a defect. To take into account the influence of random variables, the model uses the Weibull distribution. The model assumes the division of the insulation thickness into some areas, each of which is destroyed independently of the others. The destruction of these areas occurs when partial discharges occur with certain energy sufficient to destroy the material. Insulation failure is predicted using the least squares method. The results obtained can be useful in assessing the residual life of insulating materials and in conducting research in this area

This paper presents the results of research on the synthesis of aluminum alloys of the Al–Si–Mg (Ak7ch), Al–Si–Mn (AK12), Al–Si–Cu–Mg (AK6M2), and Al–Mg–Mn (AMg5) systems using dispersed waste: beverage cans (Al–Mn–Mg system), sawdust of a cast alloy (Al–Si–Mg system), and twisted chips of deformable alloys of the Al–Cu–Mg and Al–Mg–Mn systems. A study of the microstructure of waste in the initial state is performed and the typical sizes of the main phases are determined. The main criteria for the quality of recyclable waste are determined: the purity (kp), contact with the atmosphere (ka), and maximum recovery of metal (ММе). Based on the proposed criteria, the waste is graded according to recycling efficiency. The lowest total score is assigned to cans of waste. Sawdust from the AK9ch alloy had the highest score. Experiments on the synthesis of Al–Si–Mg (Ak7ch), Al–Si–Mn (AK12), Al–Si–Cu–Mg (AK6M2), and Al–Mg–Mn (AMg5) alloys have shown that the usable yield varies from 82 to 96%. The minimum yield of usable material is set for the AK12 alloy, whose charge composition is dominated by beverage-can waste. The chemical compositions of the alloys in terms of the content of the main alloying and impurity elements meets the requirements of regulatory documentations. Tests of mechanical properties have shown that the synthesized alloys have a guaranteed margin of strength and plasticity in comparison with the requirements of regulatory documentation. Based on metallographic studies, it is found that the microstructure of synthesized alloys does not contain nonmetallic inclusions and gas porosity. Unmodified and modified samples from the Al–Mg–Mn alloy (AMg5) are subjected to cold rolling in several passes until cracks form. On the sample from an unmodified alloy, cracks appear after the tenth pass. The modified alloy sample withstands 12 passes before cracking. The degree of deformation in the thickness of the sample from the unmodified alloy is 60.5%; for the modified one it is 67.2%.

Recommendations are given on designing thermosiphons (TS) prepared on the basis of the experience that the authors gained in designing more than 4000 TSs for heat-recovery steam generators and the results of long-term investigations and tests carried out to study thermohydraulic and corrosion processes in vertical and inclined TSs filled with steam-water mixture. The results of similar studies performed by other authors are analyzed. References are given to the regulations on the design of heat transfer equipment for thermal and nuclear power stations. The requirements for TS construction materials, the degree of TS filling with water, and the TS vacuum level are outlined. Whether the evacuation of TS may be abandoned was assessed. Measures are proposed to prevent depressurization on water freezing in TSs. Recommendations are given on the calculation of thermohydraulic characteristics and steam-and-gas distribution in vertical or inclined TSs. The conditions of displacement by a steam flow of noncondensable gases, including air, to the top of the condensation zone in a thermosiphon are considered. Various regimes of axial heat transport and heat transfer are described for pure steam condensation (including film condensation, bubble condensation, distribution of different regimes of steam condensation, and condensate cooling along the height of the condensation zone during “flooding”). Heat transfer in the steam condensation from an air-steam mixture (the diffusion component of thermal resistance), maximum power, and the conditions for poorer cooling of the TS heating zone (“flooding,” steam separation at the upper generatrix of the heating zone in an inclined thermosiphon) are examined. Thermosiphons feature a countercurrent flow of steam and its condensate in a single flow with the same mass flowrates. Hence, a special case of “flooding” affecting the maximum power of the thermosiphon, the effect of the incoming steam flow on the heat transfer rate during film condensation, steam-and-gas distribution in a top-plugged channel, corrosion processes in thermosiphons, and hydrogen diffusion through the thermosiphon wall should also be studied.

Molten halides can be effectively employed for electrorefining of refractory and radioactive metals with relatively negative reduction potentials and high melting temperatures. In the present study electrorefining of uranium was studied for developing pyrochemical reprocessing technology of metallized spent nuclear fuels. 3LiCl-2KCl molten salt was chosen as the working electrolyte. Uranium containing electrolytes were prepared by dissolving UCl3 in the solvent salt melt in an argon filled glove box to obtain various desired concentrations of uranium in the electrolyte. The working temperature in the refining experiments varied between 450 and 750 °C. The experiments on uranium electrorefining were carried out in a stainless steel semi-industrial water-cooled electrolyser. Crude uranium metal was loaded in a specially designed molybdenum anodic basket. Glassy-carbon crucible was used to hold the melt. Molybdenum rod was employed as a cathode. The main goal of the electrolytic refining process is obtaining high-purity uranium metal. Specific energy consumption is also very important. The results of the electrolytic refining depend on various parameters. In the present study current density, temperature, uranium concentration in the electrolyte, and specific quantity of electricity passed through the cell were selected as variables, and the current efficiently was chosen as a response factor. Dense and compact uranium deposits were obtained under low current densities, while application of relatively high current densities led to the formation of uranium dendrites. Intermediate values of current density allowed producing more coherent deposits that could be easily scraped off the cathode. Increasing temperature led to a sharp change of the cathodic deposits morphology. The reason for this is the formation of tetragonal beta-uranium instead of the low-temperature orthorhombic alpha modification. The values of cathodic current efficiency in the most of experiments confirmed the three-electron scheme of uranium reduction. Cathodic current density under certain conditions exceeded 95 %. The amount of salt retained in the cathodic deposit varied from 7 to 25 %, values typical for dendrite electrolytic metals.

The article provides study results for two samples manufactured with the MPF-4 magnesium powder by means of directed laser energy and material deposition. The authors studied microhardness and microstructure of the samples by means of optical and electronic microscopic techniques; provided results of the impact of annealing on microstructure and microhardness of the samples; and assessed the possibility of using the MPF-4 powder for manufacturing parts using 3D printing technologies.

In this paper, we review photonic methods and technologies that are promising for monitoring the ocean and atmosphere and have been implemented mainly in recent years at the Institute of Automation and Control Processes, Far Eastern Branch, Russian Academy of Sciences. We present results of lidar studies that have made it possible to understand key features of ocean – atmosphere interaction processes under continent – ocean transition conditions, which determine specific features of the atmospheric aerosol distribution, small gaseous components of the atmosphere and its optical characteristics. We consider methods and tools for combined optical and laser fluorescence monitoring of the ocean surface. Particular attention is paid to results of research on remote methods and tools for real-time laser-induced and laser fluorescence environmental monitoring of the ocean, including specialised fibre-optic probes and mobile underwater robotic systems. We present results of the development and investigation of highly sensitive, noise-proof fibre-optic hydro- and seismic/acoustic sensors for remote monitoring of the ocean and robotic systems for underwater laser protection of marine vessels, hydraulic structures and oceanographic instruments against the negative impact of biofouling.

The effect of the structure of the initial charge density in liquid and solid states, as well as on the temperature–time parameters of the process of solidification of the AK6M2 alloy (Al–6% Si–2% Cu), is shown. To obtain a coarse-crystal charge (C charge), part of the melt is crystallized in ceramic forms in a sand backfill with a cooling rate of ~0.5–1.0°C/s. The fine-crystal charge (F charge) in the form of thin ingots weighing 0.2–0.3 kg is obtained by crystallization of the melt in cast-iron cold molds with ~5.0–10°C/s. Further, the charge billets are separately melted, re-refined and degassed, and the samples are poured to determine the gas content and density in the liquid (dL) and solid (dS) states. It is established that structural information from the original charge of the alloy is stable in the solid–liquid–solid system. Direct thermal analysis is used to find that the melt obtained from the F charge hardens at low temperatures: the decrease in liquidus temperature tL is 3°C; the temperature of the beginning of solidification of the eutectic is reduced by 10°C, and the temperature of the end of solidification of a eutectic is 3°C in comparison with the melt of the C charge. At the same time, the formation of α-Al and eutectic dendrites in the melt from the F charge occurs 0.4 and 0.6 min more quickly, respectively. The results obtained on the Paraboloid-4 installation show that a smaller number of pulses throughout the studied temperature range passes through the melt from the F charge, which confirms its increased density when compared to the alloy from the C charge. Thus, for the melt from the F charge, the values of the degrees of compaction were –ΔJl ~ 278.66 and –ΔJe ~ 129.83 imp/s and, for the melt from the C charge, –ΔJl ~ 302.9 and –ΔJe ~ 163.47 imp/s. The values of the phase-transition temperatures determined by anomalies on the temperature dependence Jt practically coincide with the results of direct thermal analysis. The main technological recommendations of management by structural information in aluminum alloys are formulated from the position of the phenomenon of structural heredity.

The paper provides the results obtained when studying the initial charge structure effect on the density, gas content and temperature-time parameters of AK6M2 (Al-6%Si-2%Cu) alloy solidification. Coarse crystalline charge billets ( C -charge) were obtained when pouring the melt into ceramic molds with sand filling providing a cooling rate υ охл ~0.5÷ 1.0 °C/s. Finely crystalline charge billets ( F -charge) were prepared by pouring the melt to cold cast iron molds ( υ охл ~ 5÷ 10 °C/s). Charge billets obtained were separately remelted with the same temperature-time conditions, rerefined and degassed with samples taken to determine hydrogen content as well as density values in liquid and solid states. It is established that structural information inherited from the initial charge billets is stable in the solid-liquid-solid system. It was found using direct thermal analysis that the melt obtained from C -charge solidifies with a reduction in liquidus temperature by 3 °С and in the temperatures of the beginning and end of eutectic solidification by 10 °C and 3 °С, respectively, as compared to the melt obtained from C -charge. At the same time, α-Al and eutectic dendrites form in the C -charge melt 0.4 and 0.6 min faster, respectively. The results obtained at the Paraboloid-4 unit showed that the F -charge melt has higher density as compared to the C -charge alloy due to a smaller number of pulses passing through it in the studied temperature range of 750 — 450 °C. Temperature values of aluminum and eutectic dendrite formation determined by J—t temperature relationships (where J is the number of γ pulses, t is the temperature) correlate with the results of direct thermal analysis. General practical recommendations on the purposeful conservation of positive structural information in aluminum alloys are formulated in terms of the structural heredity phenomenon.

A new approach to direct quantitative detection of small molecules (haptens) by dynamic light scattering biosensing is presented. The proposed technique implements a homogeneous competitive immunoassay and is based on optical detection of specific inhibition of nanoparticle aggregation induced by the analyte in a sample. The technique performance was tested both in buffer and milk for detection of chloramphenicol - antibiotic relevant to food safety diagnostics. Good specificity, sensitivity (LOD in milk is 2.4 ng/ml), precision (4.0 ± 1.2%), ruggedness (8.3%), and 96% recovery in conjunction with a record wide dynamic range (3 orders of magnitude) of the nanosensing technique were demonstrated. Such characteristics complemented by the assay simplicity (no washing step) and a short assay time make the approach attractive for application as an analytical platform for point-of-care and field-oriented diagnostics. Graphical abstract.

The contributions from the martensitic laths, dislocations, secondary phase particles, and supersaturated solid solutions to the overall strength of the 12%Cr–3%Co–2.5%W creep-resistant steel with low N and high B contents were calculated after various heat treatments consisting of normalizing followed by medium-temperature tempering. An increase in the normalizing temperature from 1050 to 1150 °C led to an increase in the average size of the prior austenitic grains from 44 to 68 μm, but the δ-ferrite fraction did not significantly change. Medium-temperature tempering in the range of 750–800 °C ensured the formation of a tempered martensite lath structure with an average martensitic lath/subgrain size of 0.23–0.34 μm, along with a high dislocation density inside the laths/subgrains, fine secondary phase particles such as M23C6 carbides along the boundaries of the prior austenite grains, packets, blocks, and martensitic laths/subgrains, and (Ta,Nb)X carbonitrides uniformly distributed inside the matrix. After medium-temperature tempering in the range of 750–800 °C, the ferritic matrix was supersaturated with substitutional elements such as Cr, W, Mo, and Cu. An increase in the tempering temperature from 750 to 800 °C led to decreases in the yield strength and ultimate tensile strength by 16.2% and 10.5%, respectively, as well as an increase in the elongation of 43.8%. The main contributions to the overall strengthening of the steel investigated after the different heat treatment regimens produced solid solution strengthening and precipitation hardening, which were independent of the tempering temperature, as well as lath boundary and dislocation strengthening, which was strongly dependent on the tempering temperature. Different approaches for evaluating the strengthening mechanisms and their contributions to the yield strength were applied, and the results are discussed.

The article investigates partial discharges (PD) as a mechanism of insulation destruction. Some of the known mathematical models of insulation aging take into account the effect of partial discharges. These models are based on the dependence of partial discharges power on voltage, so this dependence is investigated in the article. Experimental studies of the dependence of the characteristics of partial discharges are presented. As a source of an increased level of partial discharges, a defect is used in the termination area of the 10 kV cable with XLPE insulation. The voltage range of experiments is from 8 to 15 kV. The results show the presence of a dangerous defect in the cable. Partial discharges at 8 kV are insignificant. However, 10 kV leads to the appearance of significant partial discharges. PD at 15 kV have the most devastating effect on insulation. The results are processed to assess the dependence of PD power on voltage. The resulting dependence is consistent with existing research results. However, the obtained characteristics may change over time due to the growth of the defect.

Smart materials that can switch between different states under the influence of chemical triggers are highly demanded in biomedicine, where specific responsiveness to biomarkers is imperative for precise diagnostics and therapy. Superior selectivity of drug delivery to malignant cells may be achieved with the nanoagents that stay "inert" until "activation" by the characteristic profile of microenvironment cues (

The diagnostics of overhead power lines is an important issue in the modern electric power industry. Sometimes supporting insulators are destroyed by external factors. Cracks in insulators can cause the destruction of the insulator, which increases the electrical injuries of personnel. Therefore, the article investigates the diagnosis of insulators by the method of partial discharges as a tool for personnel protection. The electric field of normal and defective insulators is simulated. Partial discharges (PD) experiments are conducted in the same insulators. The results of modeling the electric field show a high electric field intensity in a porcelain insulator with a slit and in an epoxy insulator with a crack. In these cases, the electric field in the air gap is higher than the electric strength of the air. In other cases, the electric field is not exceed the electric strength of the material. Experimental studies have shown the highest intensity of partial discharges in cases of high electric field strength obtained in the simulation. However, other defective insulators also show the presence of partial discharges. The only case of the absence of partial discharges is a porcelain insulator without a defect. An analysis of experimental data shows that the diagnosis of partial discharges can be effective for insulators only if a voltage higher than the working voltage is used. In the experiments, only voltages of 16 kV and higher made it possible to reliably detect the presence of a defect. Therefore, this method cannot be recommended for the diagnosis of supporting insulators before the disconnector is used by personnel, which could reduce the electrical injuries of personnel. In addition, monitoring of partial discharges also will not be effective for the studied types of defects.

The article describes the study of the characteristics of partial discharges (PD) in various types of artificial defects in cable lines. A total of 13 types of insulation defects are considered. The PD measurements are carried out using a high AC voltage source and a commercial PD recorder. For each type of defect, diagrams of the amplitude-phase distribution of PD (APDPD), the average value of the apparent discharge, and the PD intensity are obtained. The results of the study show that most of the defects of insulators of overhead power lines have a relatively high intensity of partial discharges with a small average apparent charge. In the samples of cable lines, relatively high values of intensity and average apparent discharge are recorded in the presence of a defect in the end seal and a defect in the ground electrode in the form of a needle. The results obtained can be used in the development of devices for detecting defects, as well as for expanding the base of diagrams (APDPD)

The article is devoted to the technique for optimizing the structures of suspended electromagnetic separators based on the minimum weight of active materials used for their manufacture. Optimization procedure is based on output of equations of relationship of design parameters of electromagnetic separators to specified criteria. During development of the optimization technique there is used the assumption of the plane-parallel nature of the magnetic field under the pole tips of the electromagnetic separator, thanks to which the formula for magnetic force at the middle of the interpole gap is derived. The effect on the maximum magnetic force of the length of the pole tips, the inter-pole gap and the height of the suspension of the electromagnetic separator has been investigated. Based on the developed optimization methodology, an algorithm for calculating optimal structures of suspended electromagnetic separators has constructed.

The existing methods for monitoring the performance of multi-criteria fire detectors do not provide for verification of their characteristics in the conditions of transition from smoldering to flame burning. The aim of the work is the development of the research methods of the environmental parameters during the transition from smoldering (pyrolysis) to flame combustion for simulation a test fire while checking the quality of multi-criteria fire detectors.A technique to conduct research of environmental parameters under conditions of heating wood samples of different sizes to a temperature of selfignition and burning crumpled and smooth paper has been developed.Changes in the concentration of carbon monoxide, specific optical density, and scattering ability during the transition from smoldering (pyrolysis) to flame burning of prepared wood and crumpled paper were studied for the first time.It is shown that the controlled environmental parameters during the transition from smoldering pyrolysis to flame burning change together. Conclusion: the speed of growth of the scattering ability of smoke decreases by 2.4 times, the speed of increase in the specific optical density and concentration of carbon monoxide increases by 2 and 5.3 times (respec-tively), during the transition from pyrolysis to flame burning of wood.

This article presents development of magnetron sputtering technology for catalytic Pt coating production. Low Pt-loaded gas diffusion electrodes were prepared by a single-step magnetron sputtering in different regimes. Pt and Pt-carbon films (95–97 wt% Pt) were deposited directly onto the gas diffusion layers (GDLs): carbon paper (Sigracet® 39 BC) and carbon cloths (GDL-CT, ELAT® LT 1400 W). A bipolar pulsed direct current (DC) magnetron sputtering with pulsed frequency 100 kHz was used as the method for catalysts deposition. Total Pt loading in the thin films varied in the range 0.04–0.13 mg*cm−2. Obtained catalysts onto GDLs were investigated by scanning/transmission electron microscope (S/TEM), X-ray Absorption Near Edge Structure (XANES) and potentiodynamic methods. The deposited catalysts had a high electrochemical surface area (ECSA) and stability determined by the durability stress test (DST) method. The highest ECSA was obtained with Pt target in the pulsed (100 kHz) sputtering mode. This ECSA values were rather stable during 3000 cycles of stress-tests versus 500 cycles for Pt deposited by polyol method on the same gas diffusion layers.

The ever-increasing use of magnetic particle bioconjugates (MPB) in biosensors calls for methods of comprehensive characterization of their interaction with targets. Label-free optical sensors commonly used for studying inter-molecular interactions have limited potential for MPB because of their large size and multi-component non-transparent structure. We present an easy-to-use method that requires only three 20-min express measurements to determine the key parameters for selection of optimal MPB for a biosensor: kinetic and equilibrium characteristics, and a fraction of biomolecules on the MPB surface that are capable of active targeting. The method also provides a prognostic dependence of MPB targeting efficiency upon interaction duration and sample volume. These features are possible due to joining a magnetic lateral flow assay, a highly sensitive sensor for MPB detection by the magnetic particle quantification technique, and a novel mathematical model that explicitly describes the MPB-target interactions and does not comprise parameters to be fitted additionally. The method was demonstrated by experiments on MPB targeting of cardiac troponin I and staphylococcal enterotoxin B. The validation by an independent label-free technique of spectral-correlation interferometry showed good correlation between the results obtained by both methods. The presented method can be applied to other targets for faster development and selection of MPB for affinity sensors, analytical technologies, and realization of novel concepts of MPB-based biosensing in vivo.

The activity of foam ceramic and foam glass in terms of the silicate-alkali interaction in concrete was investigated. It was found that in the wet environment in concrete the vitrified walls of the pores of the aggregates are chemically active. The transformations of foam ceramic include gelation of the pore walls with formation of an alkaline aluminosilicate gel followed by its crystallization. This binds the active components on such an aggregate in the crystalline phases, which are inert in a moist environment. The final stage of the transformation of the foam glass is noncrystallizing, alkaline, hydrated, silica gel.

The results of a femtosecond optical and magneto-optical spectroscopy study of a thin epitaxial film of a low-temperature magnetically soft Pd0.94Fe0.06 alloy on a ({dy001})-MgO substrate are reported. The photoinduced demagnetization and magnetization recovery times are determined. The latter increases critically at approaching the ferromagnetic ordering temperature TC = 190 K from below. It is shown that the reflectivity dynamics after a photoexcitation pulse evolves from a two-exponential in the paramagnetic phase to a four-component at 80 K < T < TC, simplifying to a three-component at T < 50 K. According to our interpretation, such an evolution, along with the manifestation of an additional increasing component in the magnetic response at 80 K < T < TC, indicates a magnetic and electronic inhomogeneity of the film associated with the distribution of local iron concentrations. The fraction of small-scale inclusions of the paramagnetic phase is estimated as ≈10 vol %.

Among different magnetic thin films, L10 FePt due to high magnetocrystalline anisotropy is attracting much attention for applications in new generation of magnetic recording media. In this work, switching time and switching mechanism of magnetization as essential properties of L10 FePt film was studied by magneto-optical Kerr effect (MOKE) and time-resolved magneto-optical Kerr effect (TR-MOKE). For this purpose, static in plane and out of plane magnetic hysteresis loop of the 20-nm thick L10 FePt film on (1 0 0) MgO was measured and modeled using polar and longitudinal MOKE and mumax code, respectively. Furthermore, the switching time of magnetization was studied using laser-induced ultrafast demagnetization and relaxation of the sample by TR-MOKE, in which for the first time, the magnetic field was applied in the plane of the sample for this measurement.

The corrosive effect of alkali in the cement (ASR interaction) on porous aggregates — foam ceramic and geofoamsitals (analogs of foam glass and foam sitals) in an alkaline medium modeling the liquid phase of setting cement was investigated. It was found that the devitrification of glass melt in the process of thermoactivated pore formation increases the ASR-tolerance of foam ceramic aggregates provided that the crystals are uniformly distributed over the wall thickness of the pores. It is shown that in an alkaline medium the active surface of foam ceramic aggregates is encapsulated by crystalline Ca-, Na-aluminosilicates and subsequent ASR interaction ceases.

The literature data on thermal behavior of crystalline nickel fluorides NiF3 and Ni2F5 in the higher oxidation states are analyzed. Their enthalpies of formation are calculated: ΔfHo(Ni[NiF6](cr), 0 K) = -1399.6 ± 6 and ΔfHo(Ni2F5(cr), 0 K) = −1370.5 ± 8 kJ/mol. The partial saturated vapor pressures in the NiF3–Ni2F5 and Ni2F5–NiF2 systems over a broad temperature range are determined. The technical impossibility to achieve a measurable pressure of NiF3 is shown. The findings are compared to the data for similar derivatives of 3d-block elements and ruthenium and platinum trifluorides. Ni2F5(cr) is suggested to be used as a fluorine accumulator.

The results of a 20-year-long longevity bench testing of nineteen full-size thermosyphons (TSs) made of steel 20 at a steam-water medium temperature of 240–265°C are presented. For the manufacture of TSs, various methods for processing the inner surface and different compositions of filling aqueous solutions have been used. The thermosyphons were periodically removed from the tests and cooled for monitoring the conditional relative vacuum $${{p}_{{{\text{vac}}}}} = 1 - {{{{p}_{0}}} \mathord{\left/ {\vphantom {{{{p}_{0}}} {{{p}_{{{\text{atm}}}}}}}} \right. \kern-0em} {{{p}_{{{\text{atm}}}}}}},$$ where $${{p}_{0}}$$ and $${{p}_{{{\text{atm}}}}}$$ are the absolute pressure in the steam-gas volume of the thermosyphon and the atmospheric pressure, respectively. The value of $${{p}_{0}}$$ was determined using a thermal method described in this paper, which does not require thermosyphon depressurization. After the last inspection of pvac, four TSs were removed from the tests. The solution contained therein was taken for the chemical analysis of its composition. For the inspection of the inner surface, samples were cut out of the pipes. For the samples of one thermosyphon, metallographic studies were performed to assess changes in the structure and mechanical properties of the pipe metal in the course of hydrogen diffusion through the pipe wall. It was revealed that 16 of 19 TSs exhibit a decrease in pvac less than 6% during the test period. A high performance was also obtained for TSs manufactured according to the economical technology reported in this paper. The oxygen-free environment inherent in the thermosyphons provide self-passivation of the thermosyphon internal surface with the formation of a protective layer of magnetite. This layer reduces the corrosion rate with releasing hydrogen up to the rate of hydrogen removal via diffusion through the wall of a carbon steel pipe. Retaining the initial vacuum, reducing the wall thickness of the thermosyphon less than by 0.1 mm, and the positive results of metallographic studies confirmed the potentialities of long-term thermosyphon operation with retaining high heat-transfer characteristics and with the absence of hydrogen influence on the structure and mechanical properties of the thermosyphon metal.

Three types of polymer-coated glass slides were prepared by acylation of their γ–aminopropyl derivatives with succinic anhydride or poly(p-nitrophenyl acylate) (PNPA) at various reaction times. The variations in duration of chemical adsorption of PNPA allowed control over nano-corrugation of the reactive surfaces employed for biosensing. The visually smooth and optically clear polymer-coated slides were used for immobilization of a conjugate of bovine serum albumin with chloramphenicol (CAP) and label-free measurement of concentration of this antibiotic. The sensor chips prepared in this way provided strong biosensing response due to fast biomolecular interactions and efficient competition of the target analyte during indirect immunoassay. The kinetics of formation and dissociation of immune complexes “conjugate-antibody” on the sensor chip surface was registered by the label-free methods of spectral-correlation and spectral-phase interferometry. The average thickness of immune complex adsorption layers was in the range of 5–12 nm. The highest value of kinetic association constant (kon = 5 × 104 M−1s−1) and the lowest equilibrium dissociation constant (Kdiss = 2 × 10-8 M−1) were achieved with the chips originated in the PNPA-coated slides, which were produced under short (2 min) polymer chemisorption and exhibited nano-corrugation almost unchanged with respect to the parent glass, according to the atomic-force microscopy. The detection limit for CAP detection was 80 pg/mL, and the dynamic range was 5 orders. The proposed methods for fabrication of sensor chips with nano-corrugated surface, the results of their characterization, as well as the developed assay can be employed for high-throughput recording of multiple molecular interactions by spectral interferometry and in a wide range of biosensing platforms for registration of biologically active compounds in medicine, veterinary, food control and ecological monitoring.

9–12%Cr martensitic steels are perspective materials for critical components of new high-efficiency power plants working at ultra-supercritical parameters of steam. Addition of 0.2% rhenium in the experimental steel improved the short-term creep strength at 650 °C. Comparison of kinetics of tungsten depletion from the matrix in different high-Cr martensitic steels showed that rhenium in the experimental 10Cr-3Co-3W-0.2Re steel did not lead to retaining an increased amount of solute W in the ferritic matrix during both aging and creep at 650 °C. At the same time, the precipitation of the high fraction of the fine Laves phase particles provided the effective particle strengthening.

Based on studies of fractional, chemical, and phase compositions of Al-containing slags of different origin, it is established that they are multicomponent systems consisting of metal and nonmetal parts. The nonmetal part includes water-soluble and water-insoluble compounds. A practical flowsheet of recycling of Al-containing slags is proposed with the purpose of its further use as the secondary refractory dusting material (SRDM). The positive effect of the SRDM on the quality of refractory ceramic molds for investment casting and the surface finish of aluminum pilot castings is established. Its use promotes a ninefold increase in strength of refractory ceramic molds when compared with the quartz sand mold and an increase in gas permeability by 15 and 33% when compared with molds made of fused alumina and quartz sand, respectively. The formation of refractory ceramic mold formed based on the SRDM is investigated. The interaction mechanism of the dusting material particles with the suspension is substantiated from the viewpoint of colloidal chemistry. When forming the layers of the ceramic mold using the SRDM, negatively charged aluminum hydroxide micelles are formed. The interaction of oppositely charged Al(OH)3 and SiO2 micelles promotes the close engagement of the secondary refractory dusting material particles to each other. The theoretical substantiation of the formation of the ceramic mold layers with the application of the SRDM makes it possible to explain the decrease in the roughness characteristics on the surface of AK9ch alloy castings for the investment casting by a factor of 3.7 when compared with standard production processes.

Electron paramagnetic resonance (EPR) study of the impurity Gd3+ ions in the multi-site SrY2O4 crystal isostructural to the magnetically-frustrated SrGd2O4 compound is reported. Analysis of the angular dependences of the EPR spectra at room temperature allowed us to establish the spin-level energy patterns in the ground states of the Gd3+ ions at the Y(1) and Y(2) sites. Parameters of the spin-Hamiltonian in the frames related to the crystal axes and to the principal center axes are determined.

The studies of fractional, chemical and phase compositions of aluminum-containing slags of different origin found that slags are multi-component systems consisting of metal and non-metal parts. The non-metal part contains water-soluble and water-insoluble components. A practical scheme for recycling aluminum-containing slags was proposed in order to isolate the water-insoluble component to be further used a secondary refractory dusting material. It was found that the secondary refractory dusting material has a positive effect on the quality of refractory ceramic molds in investment casting and the surface finish of experimental aluminum castings. This material improves the strength of refractory ceramic molds by 9 times in comparison with silica sand molds and increases gas permeability by 15 % to 33 % in comparison with fused alumina and silica sand molds, respectively. The study covers the processes used to produce refractory ceramic molds based on the secondary refractory dusting material. The mechanism of interaction between dusting material particles and suspension is theoretically justified in terms of colloid chemistry. Negatively charged aluminum hydroxide micelles appear when ceramic mold layers are formed using the secondary refractory dusting material. Interaction between differently charged Al(OH)3 and SiO2 micelles makes secondary refractory dusting material particles come in close contact with each other. The theoretically justified processes of ceramic mold layer formation with the secondary refractory dusting material make it possible to explain the reduction in the surface roughness of castings made of AK9ch aluminum casting alloy using investment casting by 3.7 times compared with standard production processes.

Solders of the Al–Cu–Si system (A34 brand) and Zn–Al–Cu system (Welco52 brand) are investigated. It is found that the A34 solder (Al–28% Cu–6% Si) melts and crystallizes in a narrow temperature range (~18°C). Solidus and liquidus temperatures of the A34 solder are ~508 and ~526°С, respectively. Solders of the Zn–Al–Cu system (Zn–4% Al–2.5% Cu) have an eutectic composition that provides melting and crystallization at a constant temperature of ~389°С. Densities of studied solders in liquid and solid states are investigated. Their values for the solder of the A34 brand are 3.02 and 3.32 g/cm3, respectively, and, for the zinc solder, 6.28 and 6.69 g/cm3. The influence of casting conditions on the structure of cast alloys in the form of rods with a cross-section area of 13, 10, and 5 mm2 is investigated. The main structural components of solder alloys refine with a decrease in the cross-section area. Dendrites of the aluminum-based solid solution and CuAl2 phase refine in the microstructure of the A34 solder. Dendrite sizes of the zinc-based solid solution most noticeably decrease in the zinc solder. The largest castability is characteristic of alloys fabricated from rod solders with a cross section of 5 mm2 for studied gaps in the sampling of 2.0, 1.5, and 1.0 mm. The zinc solder of the eutectic composition has the best castability when compared with the A34 solder: this characteristic for the melt formed from the zinc-based solder rod with a cross section of 5 mm2 and a gap width in the sampling of 2.0 mm is 100% (the melt of the A34 solder formed from the rod of the same cross section has a castability of 98%). The results of experiments on soldering plates made of the AK12 alloy and sheets made of the AMts alloy show the presence of a tight boundary in the “solder–base material” system, as well as the absence of discontinuities in the form of pores and unsoldered regions. An insignificant interpenetration of solder alloys into the base material is observed, especially when soldering cast plates made of the AK12 alloy.

The study covers Al–Cu–Si (A34 grade) and Zn–Al–Cu (Welco52 grade) solders. It is found that A34 solder (Al–28%Cu–6%Si) melts and crystallizes in a narrow range of temperatures (~18 °C). Solidus and liquidus temperatures of A34 solder are ~508 °С and ~526 °С, respectively. Zn–Al–Cu (Zn–4%Al–2,5% Cu) solder has a eutectic composition, so it melts and crystallizes at a constant temperature of ~389 °С. Densities of investigated solders in their liquid and solid states are studied. A34 solder has a density of 3,02 and 3,32 g/cm3 , respectively. Zinc solder density is 6,28 g/cm3 in the liquid state, and 6,69 g/cm3 in the solid state. The influence of casting conditions on the structure of cast alloys in the form of bars with cross sections of 13, 10, and 5 mm2 was investigated. Main structural components of solder alloys reduce in size as cross sections decrease. The aluminium-based solid solution dendrites and CuAl2 phase are reduced in the A34 solder microstructure. In zinc solders, the most severely reduced ones are zinc-based solid solution dendrites. The best castability is observed in melts obtained from 5 mm2 section bar solders with studied sample gaps of 2,0, 1,5 and 1,0 mm. Eutectic zinc solder features better castability in comparison with A34: castability of the melt obtained from the 5 mm2 section zinc solder rod with a sample gap width of 2,0 mm is 100 % (for A34 melt solder obtained from a rod of the same cross section it was 98 %). Experiments on soldering AK12 alloy plates and 3003 alloy sheets demonstrated that there is a tight border in the solder/base material system and no any defects such as pores or unsoldered areas. There was a slight interpenetration of solder alloys into base materials, especially when soldering AK12 cast plates.

In this work, we report a novel method of label-free detection of small molecules based on direct observation of interferometric signal change in graphene-modified glasses. The interferometric sensor chips are fabricated via a conventional wet transfer method of CVD-grown graphene onto the glass coverslips, lowering the device cost and allowing for upscaling the sensor fabrication. For the first time, we report the use of graphene functionalized by the aptamer as the bioreceptor, in conjunction with Spectral-Phase Interferometry (SPI) for detection of ochratoxin A (OTA). In a direct assay with an OTA-specific aptamer, we demonstrated a quick and significant change of the optical signal in response to the maximum tolerable level of OTA concentration. The sensor regeneration is possible in urea solution. The developed platform enables a direct method of kinetic analysis of small molecules using a low-cost optical chip with a graphene-aptamer sensing layer.

Label-free approach is developed based on the spectral-correlation and spectral-phase interferometric methods for characterization and fine-tuning of bi-functional ligands, which can improve the limits of detection of immunoassays by several orders of magnitude. The concept was verified by development and optimization of an ultrasensitive test system for registration of thyroxine (a marker of thyroid diseases).

Rapid multiplex methods were proposed for simultaneous measurements of concentrations of a number of different molecular markers of cancer in clinical samples. Low coherent interferometry was used for controllable design of intermolecular interface layers. A unique combination of magnetic nanolabels, original high-sensitive electronic readers, and a variety of 3D porous solid phases for biochemical assays were employed.

A simple model is designed for an inductive immunosensor in which the magnetic particles are attached to the bioreceptors to form a sandwich on the surface of an inductor. The inductor consists of a coil covered on a silicon oxide wafer. The coil comprises 250 turns of a planar gold wire, which is approximately 200 nm thick and 392 mm long, placed in a circle with a diameter of 2 mm. The model is well characterised by controlling the geometrical and electrical parameters and also the permeability of the magnetic material. To evaluate the feasibility of the model for virus monitoring, a novel inductive immunosensor is designed and for the first time applied for the detection of hepatitis B surface antigen (HBsAg). At first, Fab′ segment of primary anti-HBsAg is immobilised on the coil. Then, the coil is exposed to HBsAg and the complex is introduced to a secondary antibody conjugated with magnetic particles to form an immune-sandwich. Finally, the influence of magnetic particles on the coil inductance is recorded and used as a signal for HBsAg detection. The magnetic inductive immunosensor showed specific responses toward HBsAg with the detection limit of 1 ng mL−1, linear range of 1 to 200 ng mL−1, and a sensitivity of 6 × 10−4 mL ng−1. The experimental results showed a very good agreement with simulation data indicating the compatibility of sensor sensitivity to the expected theoretical values.

A comparative study on the influence of fabrication methods of AlTi4 master alloys on the grain size of Al3Ti intermetallic compounds is performed. It is found that an increase in the cooling rate during the solidification from 10–15 K/s (the crystallization in a hot cast iron mold and plate 30 mm in thickness) to 60–65 K/s (the crystallization in a cold cast iron chill mold; the rod 20 mm in diameter and 170 mm in length) promotes an increase in length and thickness of needle crystals of intermetallic compounds almost twofold (from 397 × 23 to 215 × 13 μm). Herewith, a decrease in electrical conductivity and an increase in the master alloy density in the solid state are observed. The modification of the master alloy melt by the addition of magnesium in an amount of 0.5 wt % determines the formation of homogeneous fine needles of intermetallic compounds 98 × 3 μm in size. The magnesium addition insignificantly decreases electrical conductivity and density when compared with the AlTi4 master alloy crystallized at the same cooling rate (60–65 K/s). The grain refinement of aluminum of the A97 grade and AK9ch alloy (the Al–Si–Mg system) by these foundry alloys with the same amount of introduced titanium (0.01 wt %) exert hereditary influence on the density and electrical conductivity, as well as on the marcograin (A97) and aluminum dendrites (AK9ch). The maximal modifying effect is characteristic of the AlTi4 master alloy containing magnesium in an amount of 0.5 wt %. Its introduction into the alloy promotes the formation of aluminum dendrites of 10 μm in size in an amount of 1427 pieces/mm2 in the alloy structure. When modifying the AK9ch alloy by the master alloy crystallized with cooling rates of 10–15 K/s, dendrites 28 μm in size in an amount of 672 pieces/mm2 are formed in the alloy structure. It is proposed to use the determination procedures of density and electrical conductivity for the express evaluation of the modifying efficiency of master alloys.

Exchange-coupled BiFeO3/ferromagnet thin film heterostructures are promising for a fast and power efficient control of magnetization of the ferromagnetic layer. In the paper, the results of the study of magnetic properties of the epitaxial Fe2B/BiFeO3 heterostructure on (0 0 1)-SrTiO3 substrate with ferromagnetic resonance (FMR) spectroscopy are presented. The hierarchy of magnetic anisotropies that determine the angular variation of the resonance field in-plane and in-/out-of the plane of the system include the tetragonal four-fold and uniaxial terms for the Fe2B layer, uniaxial term for antiferromagnetic BiFeO3 layer and the exchange coupling at the interface. We find out that the exchange bias direction can be switched by a strong enough applied magnetic field. Both the exchange bias and an in-plane FMR resonance field of the heterostructure are strongly affected by the illumination with λ = 405 nm light. An optical tunability of the exchange bias and ferromagnetic resonance fields of the heterostructure has been demonstrated.

Unique properties of magnetic nanoparticles (MNP) have provided many breakthrough solutions for life science. The immense potential of MNP as labels in advanced immunoassays stems from the fact that they, unlike optical labels, can be easily detected inside 3D opaque porous biosensing structures or in colored mediums, manipulated by an external magnetic field, exhibit high stability and negligible background signal in biological samples, etc. In this research, the magnetic nanolabels and an original technique of their quantification by non-linear magnetization have permitted development of novel methods of multiplex biosensing. Several types of highly sensitive multi-channel readers that offer an extremely wide linear dynamic range are developed to count MNP in different recognition zones for quantitative concentration measurements of various analytes. Four approaches to multiplex biosensing based on MNP have been demonstrated in one-run tests based on several 3D porous structures; flat and micropillar microfluidic sensor chips; multi-line lateral flow strips and modular architecture of the strips, which is the first 3D multiplexing method that goes beyond the traditional planar techniques. Detection of cardio- and cancer markers, small molecules and oligonucleotides were used in the experiments. The analytical characteristics of the developed multiplex methods are on the level of the modern time-consuming laboratory techniques. The developed multiplex biosensing platforms are promising for medical and veterinary diagnostics, food inspection, environmental and security monitoring, etc.

A large number of parametric methods were proposed to calculate the characteristics of the long-term strength of metals. All of them are based on the fact that temperature and time are mutually compensating factors in the processes of metal degradation at high temperature under the action of a constant stress. The analysis of the well-known Larson-Miller, Dorn-Shcherby, Menson-Haferd, Graham-Wallace, and Trunin parametric equations is performed. The widely used Larson-Miller parameter was subjected to a detailed analysis. The application of this parameter to the calculation of ultimate long-term strength for steels and alloys is substantiated provided that the laws of exponential dependence on temperature and power dependence on strength for the heat resistance are observed. It is established that the coefficient C in the Larson- Miller equation is a characteristic of the heat resistance and is different for each material. Therefore, the use of a universal constant C = 20 in parametric calculations, as well as an a priori presetting of numerical C values for each individual group of materials, is unacceptable. It is shown in what manner it is possible to determine an exact value of coefficient C for any material of interest as well as to obtain coefficient C depending on stress in case such a dependence is manifested. At present, the calculation of long-term strength characteristics can be performed to a sufficient accuracy using Larson-Miller’s parameter and its refinements described therein as well as on the condition that a linear law in logσ–Р dependence is observed and calculations in the interpolation range is performed. The use of the presented recommendations makes it possible to obtain a linear parametric logσ–Р dependence, which makes it possible to determine to a sufficient accuracy the values of ultimate long-term strength for different materials.