Молекулярно-динамическое моделирование разрушения карбида кремния под действием внешней механической нагрузки

In this study, molecular dynamic simulations of quasi-static compression of silicon carbide nanorod, were performed. A longitudinal through defect in the form of a cylindrical channel was in- troduced into the central part of the nanorod. The influence of the cross sectional size of this internal channel on the strength properties was investigatedПредставленная работа посвящена исследованию поведения стержня карбида кремния 3C-SiC при квазистатическом сжатии. В центр стержня вносился продольный сквозной дефект в виде канала цилиндрического сечения. Было исследовано влияние поперечного размера этого внутреннего канала на прочностные характеристики стержн

X-ray Excited Optical Luminescence of Eu in Diamond Crystals Synthesized at High Pressure High Temperature

Powder diamonds with integrated europium atoms were synthesized at high pressure (7.7 GPa) and temperature (1800 °C) from a mixture of pentaerythritol with pyrolyzate of diphthalocyanine (C64H32N16Eu) being a special precursor. In diamonds prepared by X-ray fluorescence spectroscopy, we have found a concentration of Eu atoms of 51 ± 5 ppm that is by two orders of magnitude greater than that in natural and synthetic diamonds. X-ray diffraction, SEM, X-ray exited optical luminescence, and Raman and IR spectroscopy have confirmed the formation of high-quality diamond monocrystals containing Eu and a substantial amount of nitrogen (~500 ppm). Numerical simulation has allowed us to determine the energy cost of 5.8 eV needed for the incorporation of a single Eu atom with adjacent vacancy into growing diamond crystal (528 carbons)

Моделирование процесса холодного напыления термопластичного порошка

The work is devoted to the deposition of composite powder materials by cold spray method. As a spraying material, a thermoplastic compound «WAY» for marking the roadway was used. An asphalt concrete was used as a substrate. As a result of experimental studies, the dependence of the deposition efficiency on the stagnation temperature of the working air in the ejector nozzle was obtained. The ANSYS Fluent package was used for evaluative modeling of the cold spraying process. Gas flow patterns were obtained in the computational domain without particles and taking into account the interaction of the flow with particles. The trajectory of the particles was calculated for various spraying parametersРабота посвящена нанесению композиционных порошковых материалов методом холодного газодинамического напыления (ХГН). В качестве композитного материала использовался термопластичный состав для маркировки дорожного полотна ТЕРМОПЛАСТИК «WAY». В качестве материала подложки применяли дорожное полотно с асфальтобетонным покрытием. В результате экспериментальных исследований получена зависимость коэффициента напыления от температуры рабочего воздуха в эжекторном сопле. Для оценочного моделирования процесса ХГН использовался пакет ANSYS Fluent. Получены картины течения газа в расчетной области без частиц и с учетом взаимодействия потока с частицами. Рассчитана траектория частиц при различных параметрах напылени

Stability and Composition of Helium Hydrates Based on Ices I_h and II at Low Temperatures

The recently developed approach describing host lattice relaxation, guest–guest interactions and the quantum nature of guest behavior (Belosudov, R. V.; Subbotin, O. S.; Mizuseki, H.; Kawazoe, Y.; Belosludov, V. R. J. Chem. Phys. 2009, 131, 244510) has been used to derive the thermodynamic properties of helium hydrates based on ices I_h and II. The<i> p</i>–<i>T</i> phase diagrams of the helium hydrates in different ices are presented for a wide range of pressures and temperatures, and the structural transitions between pure ice I_h and ice II as well as between ice I_h-based helium hydrate and ice II-based helium hydrate have been found to be in agreement with the available experimental data. The “ice II-based helium hydrate–ice I_h-based helium hydrate” equilibrium shifts toward the higher pressures in comparison with the line of “ice II–ice I_h” equilibrium. The degrees of interstitial space filling by helium in ice I_h-based and ice II-based hydrates decrease with increasing temperature and lowering of pressure. It is demonstrated that the helium filling in ice I_h proceeds more slowly than in ice II. However, the mole fraction of helium in the hydrate based on ice I_h is significantly higher than that in the ice II-based hydrate. We predict that during the phase transition from the ice I_h-based hydrate to the ice II-based one a discharge of gaseous helium should be observed. This may serve as an indicator of the phase transition in experiment