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The paper shows the possibility of obtaining coatings from cubic tungsten carbide by the plasma dynamic method. According to X-ray phase analysis, the coating consists mainly of cubic tungsten carbide (up to 97%), hexagonal modifications - W2C and WC, also unreacted tungsten and carbon. The optimal location of the substrate relative to the cut of the graphite electrode-barrel was determined, which provides the maximum content of cubic tungsten carbide, as well as the largest deposition area, which amounted to 55÷65 mm. more...

This study is devoted to thermogravitational convection of pseudoplastic nanofluid in the cavity. The lower wall of the cavity is heat-conducting and a local heater placed on this solid wall has a constant volumetric heat generation. The cavity is filled with a mixture of carboxymethyl cellulose with water and tiny solid particles of copper oxide. The problem is described by unsteady Oberbeck-Boussinesq equations with non-primitive variables such as stream function and vorticity. In the course of the study, the influence of the volume fraction of solid nanoparticles, the height of the heat-conducting lower wall on nanofluid flow and heat transfer was analyzed. more...

Within the framework of this study, the properties of obtained ceramics based on Al2O3 by spark plasma sintering (SPS) using preceramic papers are considered. This method makes it possible to obtain ceramic materials of the required shape, as well as to regulate their physicochemical properties to the required values. A qualitative and quantitative analysis of the crystal structure of aluminum oxide samples was carried out alongside with determination of mechanical properties. more...

In this paper the structure of samples obtained by the EBM method when aluminum wire was built up on a titanium substrate in order to obtain an intermetallic compound is studied.It is shown that TiAl and Al3Ti intermetallides with high nanohardness values were formed in the samples. more...

This paper presents a study of a combined modification of silumin, which included deposition of a ZrN coating on a silumin substrate and subsequent treatment of the coating/substrate system with a submillisecond pulsed electron beam. The local temperature on the samples in the electron-beam-affected zone and the thickness of the melt zone were measured experimentally and calculated using a theoretical model. The Stefan problem was solved numerically for the fast heating of bare and ZrN-coated silumin under intense electron beam irradiation. Time variations of the temperature field, the position of the crystallization front, and the speed of the front movement have been calculated. It was found that when the coating thickness was increased from 0.5 to 2 μm, the surface temperature of the samples increased from 760 to 1070 °C, the rise rate of the surface temperature increased from 6 × 107 to 9 × 107 K/s, and the melt depth was no more than 57 μm. The speed of the melt front during the pulse was 3 × 105 µm/s. Good agreement was observed between the experimental and theoretical values of the temperature characteristics and melt zone thickness. more...

In the present work, a product of ZhS6U alloy was obtained by wire-feed electron-beam additive technology on a substrate of austenitic steel. The obtained product had the shape of a thin wall and contained 20 layers and was 4.5 cm high, had no surface macro-defects and deviations from the specified geometry. The structure of the material was represented by dendrite colonies growing epitaxially in the direction of additive growth with deviation in the direction of the electron beam motion. It is shown that in the material of the additive product there is a tenfold refinement of the structure and the main strengthening phases, compared to the raw cast material. Also, studies have shown that the foreign substrate material has no crystallographic effect on the product being formed, and its submergence is already leveled at 5 mm. more...

The submonolayer adsorption of Na onto the Cu(110) surface is studied. At small Na coverages (Θ = 0.16–0.25 ML), the substrate surface subjected to missing-row reconstruction (1 × 2) is shown to be most stable dynamically. When the coverage increases to Θ = 0.5 ML, the unreconstructed substrate surface with a c(2 × 2) sodium adlayer becomes dynamically stable. For an analysis, we used data on the equilibrium atomic configuration, the adsorption energy, the phonon spectra, the local density of phonon states, and the polarization of localized vibrational modes. All calculations were performed using the interatomic potentials obtained in terms of the embedded-atom method. The calculated frequencies of localized vibrational modes agree well with the existing experimental data. more...

Представлены результаты исследований субмикроструктуры и топологического ближнего атомного порядка аморфного поверхностного сплава на основе Ti−Ni−Тa−Zr, сформированного аддитивным способом на основе импульсного электронно-пучкового жидкофазного перемешивания систем “пленка Ti70Ta30(50 нм)/пленка Zr(100 нм)/подложка из TiNi”. Показано, что в поперечном сечении поверхностного сплава сформировалась аморфная структура толщиной 2 мкм с градиентным изменением химического состава. Обнаружено, что переходный подслой к TiNi-подложке характеризуется нанокомпозитной кристаллической структурой с преимущественным содержанием интерметаллида Ti2Ni. С применением метода построения функций радиального распределения атомов по данным электронных нанодифракций выполнено исследование топологического ближнего атомного порядка в аморфном слое. Показано, что атомная структура в аморфном поверхностном Ti−Ni−Тa−Zr-сплаве имеет кластерную природу, структурный мотив которой может быть описан в виде суперпозиции соединенных между собой общими гранями координационных многогранников, соответствующих различным кристаллическим фазам девитрификации. more...

Изследването е проведено през периода 2016–2019 г. Проследено е взаимодействието на сорта Мавруд, кл. 2, присаден върху седем лозови подложки, използвани в България. Проследен е растежа и узряването на лето- растите във вкоренилището. След изваждането на лозите от вкоренилището е отчетен добива на стандартни лози. Целта на настоящата разработка е насочена към разкриване на подходяща лозова подложка за сорта Мавруд във вкоренилището, при почвено-климатичните условия на Пловдивския район. more...

Изследването е проведено през периода 2016–2019 г. Проследено е взаимодействието на сорта Мавруд, кл. 2., присаден върху седем лозови подложки, използвани масово в България. Отчетено е калусообразуването в мястото на присаждане и петата на резниците, динамика на развитие на корени и леторасти по време на стра- тифициране. Направена е статистическа обработка на данните и са доказани различията между изследваните варианти – Мавруд/41 B; Мавруд/5 ВВ; Мавруд/ 110 R; Мавруд/140 Ru Мавруд/ Fercal; Мавруд/SO 4; Мавруд/1103 P. more...

The investigation results of elemental and phase composition, state of defective substructure and microhardness of the surface layer of «film (Ti)/substrate (SiC-ceramics)» system (Ti film 0.5 μm thick was deposited on the surface of SiC-ceramics) subjected to treatment with an intense pulsed low-energy electron beam (15 J/cm2, 200 μs, 0.3 s−1, 20 pulses) are presented. It is shown that irradiation of the «film (Ti)/substrate (SiC-ceramics)» system with an electron beam is accompanied by the formation of multielement multiphase (SiC; TiC; Ti5Si3) surface layer having submicro- and nanocrystalline structure. Microhardness of the irradiated surface layer reaches a value of 74 GPa, that is twice the value of microhardness of SiC-ceramics (36 GPa). more...

Экспериментально исследован адмиттанс МДП-структур на основе МЛЭ p-HgCdTe ( x = 0,22-0,23) в широком диапазоне частот и температур. Дифференциальное сопротивление области пространственного заряда для МДП-структуры на основе p-HgCdTe, легированного As, ограничено процессами туннельной генерации в диапазоне температур 8-100 К. Для МДП-структур на основе пленки p-HgCdTe, в которой произошла конверсия типа проводимости после отжига, сопротивление области пространственного заряда определяется генерацией Шокли-Рида в диапазоне температур 50-77 К. more...

Экспериментально исследован адмиттанс МДП-структур на основе МЛЭ p-HgCdTe ( x = 0,22-0,23) в широком диапазоне частот и температур. Дифференциальное сопротивление области пространственного заряда для МДП-структуры на основе p-HgCdTe, легированного As, ограничено процессами туннельной генерации в диапазоне температур 8-100 К. Для МДП-структур на основе пленки p-HgCdTe, в которой произошла конверсия типа проводимости после отжига, сопротивление области пространственного заряда определяется генерацией Шокли-Рида в диапазоне температур 50-77 К. more...

The fast coming of the fundamental sciences into agricultural practice had an effect on fruit growing as well. The introduction of clonal rootstocks in the production of apple trees became a turning point in its development through the creation of intensive orchard plantations. For this reason, we consider it necessary to offer summarized information about both long-time introduced and newly bred vegetative apple rootstocks, based on international and domestic investigations. more...

In this article we examined the temperature conditions in contact sputtered particle - substrate at the formation of a multi-layer thermal spray coating. The calculations of contact temperature at the interface sputtered particle - substrate for various combinations of the contacting materials were carried. Given that the temperature in the contact is an important condition for the formation of the adhesive bond coating to the substrate, we studied the possibility of using the intermediate layer for Al[2]O[3] deposition on a steel substrate. more...

The paper provides consideration to the approaches to designing new grinding tools on flexible backing - flap grinding wheels and grinding belts having abrasive grains with certain form and orientation in their structure. Methods to estimate the shape of abrasive grains have been analyzed. Experimental data has been presented how the form of a grain affects characteristics of tools on flexible backing. Recommendations on practical application of new tools have been given. more...

The paper presents formation of the substrate film system (Zr-Ti-Cu/Al) by electric arc spraying of cathode having the appropriate composition. It is shown that the intense beam radiation of the substrate film system is accompanied by formation of the multi-phase state, the microhardness of which exceeds the one of pure A7 aluminum by = 4.5 times. more...

The model for description of the initial stage of ion implantation into the surface layer of the metal is presented. The interdependence of embedded impurity concentration and deformations arising from the impact of particles on the surface is investigated. The model takes into account the particle diffusion, the finite time of mass flux relaxation; the stress appearance due to a composition change of the surface layer and a mass transfer phenomenon under a stress gradient action. It is established that the interaction of mechanical waves and concentration leads to a distribution of concentration not corresponding to a pure diffusion process. The examples of coupled problems solution for different sets of model parameters are presented. more...

The experimental setup has been designed and fabricated to study the evaporation of liquid droplets, blown by the gas flow in a mini-channel with a height of 6 and 9 mm. Substrates were removable, and the surface temperature of the substrate was maintained at a constant level. The shadow method was the main method of measurement. A series of experiments with a water drop of 100 [mu]l volume settled on a polished stainless substrate were carried out. As a result the dependences for the droplet evaporation rate were obtained in the range of temperatures 25–70 °C and Reynolds numbers of gas 0–2000. more...

The paper presents the results of theoretical and experimental studies of the interaction between a molten metal drop and a solid metal substrate and justifies measures to avoid or to weaken this interaction. more...

In this work we numerically investigate the deformation and fracture in a material with a porous ceramic coating and a polycrystalline steel substrate. The internal structure of the porous coating and microstructure of the substrate is accounted for explicitly in the calculations. To describe an internal geometry of the composite, we introduce a curvilinear mesh generation algorithm. To generate the polycrystalline structure of the substrate we use the cellular automata method with original modifications introduced. The steel substrate exhibits an elastic-plastic behavior, while the ceramic coating is elastic-brittle. To account for the grain size effect on the initial yield stress we use the Hall - Petch relationship. The boundary-value problem in the plane strain formulation is solved numerically by the finite difference method. Numerical investigations on uniaxial tension, compression, and surface loading of two-dimensional specimens are conducted. Four samples investigated are characterized by an average substrate grain size of 2, 5, 15 and 30 ?m. The complex stressstrain state taking place in loaded composite is analyzed. In the case of tension or compression, cracks are shown to originate in the local regions experiencing tensile loading. The influence of the substrate grain size on the fracture behavior of the composite is examined. more...

In this paper we studied the features of the energy balance in the system particles - substrate during thermal spraying covering. The activation energy of the atoms in the hot surface layer of the substrate was estimated. The effect of particle velocity on the activation energy of the atoms of the substrate was investigated. It is shown that in the framework of the model chosen the activation energy of the atoms of the substrate is not depended on the speed of the particles. more...

The miksing of system a film (Ti)/substrate (Al) is carried out by an intensive electron beam. The radiation modes allowing to increase microhardness and reduction in the rate of wear of material are revealed. Physical justification of this phenomenon is given. more...

Актуальность работы обусловлена совершенствованием технологии нанесения термических покрытий и методов определения оптимальных характеристик технологического процесса. Цель работы: определение температурных полей и температурных условий адгезии в модели «капля расплава - подложка» при образовании между ними металлической связи. Методы исследования: построение оригинальной математической модели температурных полей и температурного условия, соответствующих достижению адгезии в системе «капля-подложка»; экспериментальная проверка результатов, полученных по предложенной модели. Результаты. Представлен метод определения температурных полей в системе «капля-подложка», основанный на выравнивании температур малых соседних кубических объемов. Метод основан на положении, что нестационарный процесс передачи тепла приближается к стационарному процессу при уменьшении временных и размерных интервалов. В предложенном методе не используются дифференциальные уравнения. Расчет нестационарного температурного поля проводится на основе уравнений передачи тепла для стационарного режима. Для начальной контактной температуры при известных для неё величинах теплопроводности, теплоемкости и плотности металлов капли и подложки получено расчетное температурное условие, определяющее наличие или отсутствие адгезии капли. Определено, что условием наличия адгезии является плавление материала подложки под каплей. Плавление части поверхности под каплей соответствует неполной адгезии, плавление всей поверхности подложки под ней соответствует максимальной адгезии. Температурное условие адгезии справедливо при отсутствии образования интерметаллида между материалом капли и подложки. Адекватность температурного условия адгезии подтверждается наличием и отсутствием адгезии при осаждении на оловянную и свинцовую подложки капель олова и свинца. The relevance of the discussed issue is caused by the need to advance thermal spray technology and the methods for determining the process best performance. The main aim of the study is to determine thermal fields and adhesion temperature conditions in the model «liquid-alloy droplet - substrate». The methods used in the study: the mathematical modeling for thermal fields and adhesion temperature conditions in the model «liquid - alloy droplet - substrate»; experimental validation of the results calculated with the proposed model. The results. The paper introduces the method for determining thermal fields in the model «liquid-alloy droplet - substrate» based on equalization of temperatures of fixed identical small size neighboring cubic volumes. The method is based on the concept that non-steady process of thermal heating approaches to steady-state process as time and dimensional gaps are reduced. The provided method is free from using differential equations. The calculation of non-steady thermal field is based on thermal transmission equation (algebraic equations). Adhesion temperature conditions for a droplet impacting on a solid surface are obtained. The thermal condition of adhesion is based on substrate melting. Partial adhesion corresponds to melting of the part of substrate surface, total adhesion corresponds to melting of the whole substrate surface. The proposed thermal adhesion condition is valid in case of lack of intermetallic compounds formation between spat and substrate materials. The calculated results are in accordance with the experimental data. more...

Computer simulation of temperature fields formed in the radiation of system film/substrate intense electron beam irradiation. Essential distinctions in formation of a temperature field in films of the titan located on aluminum and in a massive sample of the titan are revealed. more...

The pseudoepitaxial growth of amorphous anodic alumina with ordered porous structure within single crystal grains of aluminum substrates is an amazing feature of the self-organization process, which occurs during anodization. Here, we used single crystal Al(100), Al(110), and Al(111) substrates to inspect the effect of aluminum crystallography on anodization rates and the morphology of the resulting alumina films grown under different anodization conditions. The difference in the kinetics of porous film growth on various substrates is described in terms of the activation barrier of aluminum atom release from the metal surface to the oxide layer. Scanning electron microscopy and small-angle X-ray scattering are applied for quantitative characterization of different kinds of ordering in anodic alumina films. The highest number of straight channels was found in porous anodic alumina grown on Al(100) substrates, whereas Al(111) was proved to induce the best orientational order in anodic alumina with the formation of the single-domain-like structures. Based on the obtained results, possible pathways for crystallographic control of the anodic alumina porous structure for different practical applications are discussed. more...