Why Are Alkali Halide Solid Surfaces Not Wetted By Their Own Melt?

Alkali halide (100) crystal surfaces are anomalous, being very poorly wetted by their own melt at the triple point. We present extensive simulations for NaCl, followed by calculations of the solid-vapor, solid-liquid, and liquid-vapor free energies showing that solid NaCl(100) is a nonmelting surface, and that its full behavior can quantitatively be accounted for within a simple Born-Meyer-Huggins-Fumi-Tosi model potential. The incomplete wetting is traced to the conspiracy of three factors: surface anharmonicities stabilizing the solid surface; a large density jump causing bad liquid-solid adhesion; incipient NaCl molecular correlations destabilizing the liquid surface. The latter is pursued in detail, and it is shown that surface short-range charge order acts to raise the surface tension because incipient NaCl molecular formation anomalously reduces the surface entropy of liquid NaCl much below that of solid NaCl(100).Comment: 4 pages, 3 figure

Cr2O3/Al-Al2O3 composite catalysts for hydrocarbons dehydrogenation prepared from aluminum nanopowder

Aluminum nanopowder (10–150 nm) was treated hydrothermally in mild conditions (60–95 °C, at atmospheric pressure), and an aluminum-alumina composite with high porosity and specific surface area was obtained. Cr2O3/Al-Al2O3 catalysts were prepared using the aluminum-alumina composite by impregnation techniques and tested in dehydrogenation of C4-hydrocarbons. It was shown that aluminum-alumina composites had high chemical and phase purity, specific surface area of 150–350 m2/g and the average pore size of 8–13 nm, that is favorable for application as support for catalysts. Cr2O3/Al-Al2O3 catalysts had high activity and selectivity in dehydrogenation of n- and i-butane (conversion of 44–80 mol.% and selectivity >85% at temperatures of 540–610 °C), that is comparable ones for commercial catalysts for CATOFIN, STAR processes

Mathematical model and software for investigation of internal ballistic processes in high-speed projectile installations

This paper describes a software package that allows to explore the interior ballistics processes occurring in a shot scheme with bulk charges using propellant pasty substances at various loading schemes, etc. As a mathematical model, a model of a polydisperse mixture of non-deformable particles and a carrier gas phase is used in the quasi-one-dimensional approximation. Writing the equations of the mathematical model allows to use it to describe a broad class of interior ballistics processes. Features of the using approach are illustrated by calculating the ignition period for the charge of tubular propellant

Charging Induced Emission of Neutral Atoms from NaCl Nanocube Corners

Detachment of neutral cations/anions from solid alkali halides can in principle be provoked by donating/subtracting electrons to the surface of alkali halide crystals, but generally constitutes a very endothermic process. However, the amount of energy required for emission is smaller for atoms located in less favorable positions, such as surface steps and kinks. For a corner ion in an alkali halide cube the binding is the weakest, so it should be easier to remove that atom, once it is neutralized. We carried out first principles density functional calculations and simulations of neutral and charged NaCl nanocubes, to establish the energetics of extraction of neutralized corner ions. Following hole donation (electron removal) we find that detachment of neutral Cl corner atoms will require a limited energy of about 0.8 eV. Conversely, following the donation of an excess electron to the cube, a neutral Na atom is extractable from the corner at the lower cost of about 0.6 eV. Since the cube electron affinity level (close to that a NaCl(100) surface state, which we also determine) is estimated to lie about 1.8 eV below vacuum, the overall energy balance upon donation to the nanocube of a zero energy electron from vacuum will be exothermic. The atomic and electronic structure of the NaCl(100) surface, and of the nanocube Na and Cl corner vacancies are obtained and analyzed as a byproduct.Comment: 16 pages, 2 table, 7 figure

The influence of deposition technological process parameters on surface properties of multilayer coatings

The surface of material plays a basic role in determining of various processes such dyeing penetration, chemical absorption, biocompatibility and others. At present study the surface parameters investigation for various multilayer coating types TiN, CrN, (Ti,Cr)N, TiN/TiC₁₀N₉₀, TiN/TiC₂₀N₈₀ and oxide Al₂O₃ films deposited by means Arc-PVD technology and Reactive Magnetron Sputtering (RMS) methods on the stainless steel (1H18N9) has been made. The surface thickness, roughness, topography, surface free energy (SFE) was evaluated for next conclusions about surface properties of multilayer coatings.Поверхні матеріалів відіграють значну роль в проходженні багатьох процесів, таких як фарбування, хiмiчна абсорбція, бiосумiснiсть та інші. Представлено результати проведених досліджень поверхневих параметрів багатошарових покриттів TiN, CrN, (Ti,Cr)N, TiN/TiC₁₀N₉₀, TiN/TiC₂₀N₈₀, а також оксидів Al₂O₃, які нанесено за допомогою методів Arc-PVD та реактивного магнетронного розпилення (РМР) на сталь (1H18N9). Проведена оцінка товщини, шорткiстi, топографії, поверхневої енергії та інших поверхневих властивостей багатошарових покриттів.Поверхность материалов играет определяющую роль в прохождении многих процессов, таких как окрашивание, химическая абсорбция, биосовместимость и другие. Представлены результаты проведенных исследований поверхностных параметров многослойных покрытий TiN, CrN, (Ti,Cr)N, TiN/TiC₁₀N₉₀, TiN/TiC₂₀N₈₀, а также оксидных Al₂O₃ пленок, нанесенных методами Arc-PVD и реактивного магнетронного распыления (РМР) на сталь (1H18N9). Проведена оценка толщины, шероховатости, топографии, поверхностной энергии и других поверхностных свойств многослойных покрытий

The corrosion properties of multilayer coatings deposited on stainless steel and Ti4Al6V substrates

Stainless steel (SS), titanium (Ti) and its alloys are the most widely used for clinical applications. The surface modification of metals with ceramic coatings by means of modern plasma methods is perspective way to reduce corrosion, to achieve better biocompatibility and to improve the performance of medical devices. The comparative analysis of the TiN, ZrO₂, Al₂O₃ and multilayer nitride/oxide coatings adhesion properties, hardness, elastic modulus, thickness, and corrosion resistance parameters at 05 N NaCl and SBF solution was made.Нержавіюча сталь та титанові сплави широко використовуються в сучасній медицині. Поверхнева модифiкацiя металів шляхом нанесення керамічних покриттів сучасними плазмовими методами э перспективним напрямком з метою зменшення корозії та покращення бiосумісності та ефективності застосування медичних приладів. Виконано порівняльний аналіз наступних властивостей плівок: адгезії, твердості, пружних модулів, корозійних властивостей різних багатошарових оксидних та нітридних покриттів.Нержавеющая сталь и титановые сплавы широко применяются в современной медицине. Поверхностная модификация металлов путем нанесения керамических покрытий современными плазменными методами является перспективным направлением для уменьшения коррозии, повышения биосовместимости и эффективности применения медицинских изделий. Проведен сравнительный анализ следующих свойств пленок: адгезии, твердости, упругих модулей, коррозионных характеристик различных многослойных нитридных и оксидных покрытий

Features of Physical Training Student Engineers

Вопрос профессиональной физической подготовки актуален в наше время, особенно в процессе обучения будущих инженеров. Представленные опыт и идейные позиции студентов и преподавателей Технического университета УГМК связанные с особенностями физической подготовки студентов-инженеров, а также разработанные на основе анализа деятельности специалистов в данной сфере деятельности индивидуальные комплексы физических упражнений позволили повысить уровень теоретических знаний и физической подготовленности обучающихся Технического университета УГМК направлений подготовки Горное дело, Технологические машины и оборудование, Электроэнергетика и электротехника, Металлургия и Автоматизация технологических процессов и производств

Simulation of high-speed interaction between impactor and layered-spaced design involving explosive

In this paper we present calculating and experimental study of high-speed interaction between explosive content, protected by layered-spaced design, and the cermet impactor in wide speed range. An experimental technique and mathematical model of during the behavior of explosives, protected by layer-spaced design, by with high-speed impact. The process of the interaction between the cermet impactor and element of the protective design is customized and depends on the materials of the interacting bodies, the speed and angle of impact