Thermodynamic properties and electrical conductivity of strongly correlated plasma media

We study thermodynamic properties and the electrical conductivity of dense hydrogen and deuterium using three methods: classical reactive Monte Carlo (REMC), direct path integral Monte Carlo (PIMC) and a quantum dynamics method in the Wigner representation of quantum mechanics. We report the calculation of the deuterium compression quasi-isentrope in good agreement with experiments. We also solve the Wigner-Liouville equation of dense degenerate hydrogen calculating the initial equilibrium state by the PIMC method. The obtained particle trajectories determine the momentum-momentum correlation functions and the electrical conductivity and are compared with available theories and simulations

Suppression of ablation in femtosecond double pulse experiments

We report the physical reasons of a curious decrease in the crater depth observed for long delays in experiments with femtosecond double pulses. Detailed hydrodynamic modeling demonstrates that the ablation mechanism is dumped when the delay between the pulses exceeds the electron-ion relaxation time. In this case, the interaction of the second laser pulse with the expanding target material leads to the formation of the second shock wave suppressing the rarefaction wave created by the first pulse. The evidence of this effect follows from the pressure and density profiles obtained at different delays after the first laser pulse.Comment: Submitted to one of the APS Journal

Investigation of the Degree of Local Structural Similarity between the Parent-liquid and Children-crystal States for a Model Soft Matter System

We investigate the degree of local structural similarity between the parent-liquid and children-crystal states for a model soft-matter system of particles interacting through the harmonic-repulsive pair potential. At different pressures, this simple system crystallizes into several significantly different crystal structures. Therefore, the model is well suited for addressing the question under consideration. In our studies, we carefully analyze the developments of the pair and triple correlation functions for the parent-liquid as the pressure increases. In particular, these considerations allow us to address the similarities in the orientational orderings of the corresponding liquid and solid phases. It is demonstrated that the similarities in the orientational ordering between the two states extend beyond the first and second neighbors. Currently, it is widely accepted that orientational ordering is important for understanding the behaviors of liquids, supercooled liquids, and the development of detailed theories of the crystallization process. Our results suggest that, up to a certain degree, it might be possible to predict the structures of the children-solids from studies of the parent-liquids. Our results raise anew a general question of how much insight into the properties of the liquid-state can be gained from drawing a parallel with the solid-state. © 2021 Elsevier B.V.This document is the results of the research project funded by the Russian Science Foundation (RNF-grant 18-12-00438).This work was supported by the Russian Science Foundation (grant 18-12-00438). We gratefully acknowledge access to the following computational resources: Supercomputing Center of Novosibirsk State University (http://nusc.nsu.ru), the federal collective usage center "Complex for Simulation and Data Processing for Mega-science Facilities" at NRC "Kurchatov Institute" (http://ckp.nrcki.ru/), supercomputers at Joint Supercomputer Center of Russian Academy of Sciences (http://www.jscc.ru), and ?Uran? supercomputer of IMM UB RAS (http://parallel.uran.ru)

Structure of the Simple Harmonic-Repulsive System in Liquid and Glassy States Studied by the Triple Correlation Function

An efficient description of the structures of liquids and, in particular, the structural changes that happen with liquids on supercooling remains to be a challenge. The systems composed of soft particles are especially interesting in this context because they often demonstrate non-trivial local orders that do not allow to introduce the concept of the nearest-neighbor shell. For this reason, the use of some methods, developed for the structure analysis of atomic liquids, is questionable for the soft-particle systems. Here we report about our investigations of the structure of the simple harmonic-repulsive liquid in 3D using the triple correlation function (TCF), i.e., the method that does not rely on the nearest neighbor concept. The liquid is considered at reduced pressure (P = 1.8) at which it exhibits remarkable stability against crystallization on cooling. It is demonstrated that the TCF allows addressing the development of the orientational correlations in the structures that do not allow drawing definite conclusions from the studies of the bond-orientational order parameters. Our results demonstrate that the orientational correlations, if measured by the heights of the peaks in the TCF, significantly increase on cooling. This rise in the orientational ordering is not captured properly by the Kirkwood's superposition approximation. Detailed considerations of the peaks' shapes in the TCF suggest the existence of a link between the orientational ordering and the slowdown of the system's dynamics. Our findings support the view that the development of the orientational correlations in liquids may play a significant role in the liquids' dynamics and that the considerations of the pair distribution function may not be sufficient to understand intuitively all the structural changes that happen with liquids on supercooling. In general, our results demonstrate that the considerations of the TCF are useful in the discussions of the liquid's structures beyond the pair density function and interpreting the results obtained with the bond-orientational order parameters. © 2020 IOP Publishing Ltd.This work was supported by the Russian Science Foundation (Grant 18-12-00438). We gratefully acknowledge access to the following computational resources: Supercomputing Center of Novosibirsk State University (http://nusc.nsu.ru), the federal collective usage center ‘Complex for Simulation and Data Processing for Mega-science Facilities’ at NRC ‘Kurchatov Institute’ (http://ckp.nrcki.ru/), supercomputers at Joint Supercomputer Center of Russian Academy of Sciences (http://jscc.ru), and ‘Uran’ supercomputer of IMM UB RAS (http://parallel.uran.ru)

Перспективы развития вузовских библиотек в научной информационной среде

The author systematize history of Russian university libraries, analyze their progressing in digital environment, and discuss new possibilities for modernizing education and academic libraries, in particular. The laws and regulations for university libraries are reviewed; their functions and services are specified. As a result of global information processes intensive growth, the demand for elibraries and their services have been increasing. The students of Cherepovets State University were surveyed on the issues of library service efficiency. The survey proved the significance and relevance of library services for the students; the strengths and weaknesses of library services were identified. The authors emphasize the need for intensifying marketing component in library activities and promotion of its services, and for studying target audience demands. The prospects for academic libraries are also discussed.Авторы статьи систематизируют исторические этапы развития университетских библиотек в России; анализируют поступательные изменения, происходящие в деятельности библиотек университетов в условиях цифровой среды; отмечают влияние цифрового развития общества на открытие новых возможностей для модернизации не только образовательной сферы, но и вузовских библиотек. В статье отражена нормативно-правовая база деятельности российских вузовских библиотек, уточнены их функции и направления работы. Отмечено, что развитие электронных библиотек стало следствием интенсивного развития мировых информационных процессов, в результате чего спрос на этот вид услуг продолжает расти. Приведены результаты опроса студентов относительно эффективности работы библиотечных сервисов на примере библиотеки Череповецкого государственного университета. Опрос подтвердил важность и актуальность услуг библиотеки для студентов. Выявлены слабые и сильные стороны организации услуг библиотеки, подчёркнута необходимость: усиления маркетинговой составляющей в деятельности библиотеки и продвижении её услуг, изучения запросов целевой аудитории. Изложены дальнейшие перспективы развития вузовских библиотек

Effect of Mechanical Activation on Ti3AlC2 Max Phase Formation under Self-Propagating High-Temperature Synthesis

In this study, we have investigated the effect of various mechanical activation (MA) modes on phase and structure formation in powder mixtures made up to produce Ti3AlC2 MAX phase. The optimal MA duration has been established which results in the maximum heat release under SHS due to accumulation of structural defects leading to the growth of internal energy. The effect of MA on the character and kinetics of combustion front propagation has been investigated. It was shown that following pretreatment of a powder mixture in a planetary ball mill, the combustion mode changes from stationary to a pulsating combustion and, consequently, the combustion rate decreases. The burning-out of the sample is partial and with interruptions (depressions). Force SHS-pressing technology was used for obtaining of compacted samples with homogeneous structure based on Ti3AlC2

Влияние частичного замещения титана его гидридом на структуру и свойства жаропрочного сплава TNM-B1, полученного методом горячего изостатического прессования СВС-порошка

This paper investigates the influence of partial substitution of titanium by its hydride on the microstructure and mechanical properties of TNM-B1 alloy obtained by powder metallurgy technology. The impact of the Ti:TiH2 ratio in the reaction mixture and heat treatment modes on the microstructure and mechanical properties of TNM-B1+1%Y2O3 alloy, obtained using high-energy ball milling (HEBM), selfpropagating high-temperature synthesis (SHS), and hot isostatic pressing (HIP) methods, has been examined. It was observed that a 10 % substitution of titanium with its hydride in the reaction mixtures reduces the oxygen content in SHS products from 1 % to 0.8 % due to the generation of a reducing atmosphere during the decomposition of TiH2 in the combustion wave. When the Ti : TiH2 ratio is 90 : 10, highest mechanical properties of TNM-B1+1%Y2O3 alloy were achieved: a compressive strength (σu) of 1200±15 MPa and a yield strength (YS) of 1030±25 MPa. An increase in the proportion of TiH2 results in a higher content of oxygen impurity, leading to the formation of Al2O3, which reduces the strength and ductility of the material. With additional heat treatment of TNM-B1+1%Y2O3 alloy, the globular structure transforms into a partially lamellar one, leading to an increase in σu by 50–300 MPa, depending on the TiH2 content. This attributed to a decrease in the average grain size and a reduction in dislocation mobility during deformation.В работе исследовано влияние частичного замещения титана его гидридом на микроструктуру и механические свойства сплава TNM-B1, полученного по технологии порошковой металлургии. Рассмотрено влияние соотношения Ti:TiH2 в реакционной смеси и режимов термообработки на микроструктуру и механические свойства сплава TNM-B1+1%Y2O3, полученного с использованием методов высокоэнергетической механической обработки (ВЭМО), самораспространяющегося высокотемпературного синтеза (СВС) и горячего изостатического прессования (ГИП). Установлено, что 10 %-ное замещение титана его гидридом в реакционных смесях позволяет уменьшить содержание кислорода в СВС-продуктах с 1 до 0,8 % благодаря созданию восстановительной атмосферы при разложении TiH2 в волне горения. При соотношении Ti : TiH2 = = 90 : 10 достигнуты максимальные механические свойства сплава TNM-B1+1%Y2O3: прочность при сжатии σв = 1200±15 МПа и предел текучести σ0,2 = 1030±25 МПа. Рост доли TiH2 увеличивает содержание примесного кислорода, приводящего к образованию Al2O3, который снижает прочность и пластичность материала. За счет дополнительной термообработки сплава TNM-B1+1%Y2O3 глобулярная структура преобразуется в частично ламеллярную, что приводит к увеличению σв на 50– 300 МПа в зависимости от содержания TiH2. Получаемый эффект обусловлен уменьшением среднего размера зерен и снижением подвижности дислокаций при деформации

ИССЛЕДОВАНИЕ ТОНКИХ ПОКРЫТИЙ В СИСТЕМЕ Si–B–C–N, ПОЛУЧЕННЫХ С ПОМОЩЬЮ МАГНЕТРОННОГО РАСПЫЛЕНИЯ МИШЕНЕЙ SiBC

Amorphous thin-film Si–B–C–(N) coatings are fabricated by magnetron sputtering of sintered Si–B–C targets. The coating structure is investigated using X-ray phase analysis, scanning and transmission electron microscopy, scanning probe microscopy, glow-discharge optical emission spectroscopy, and Raman spectroscopy. Mechanical and tribological properties of coatings are determined using nanoindentation, scratch testing, and pin-on-disc testing. The oxidation resistance of coatings is investigated in a temperature range of 1200–1600 °C. It is established that coatings of the optimal composition possess hardness of 20 GPa, elasticity modulus of 210 GPa, elastic recovery of 53 %, friction coefficient of 0,6 against cemented carbide ball, and oxidation resistance above 1200 °C due to the formation of the SiO2-based protective film on their surface. Coatings deposited by sputtering the target of the Si70B25C composition in Ar + 15%N2 medium showed oxidation resistance both under long-term heating at t = 1200 °C for 12 h and short-term heating at temperatures of 1400, 1500, and 1600 °C.Методом магнетронного распыления спеченных мишеней Si–B–C получены аморфные тонкопленочные покрытия Si–B–С–(N). Структура покрытий исследована с применением рентгенофазового анализа, растровой и просвечивающей электронной микроскопии, сканирующей зондовой микроскопии, оптической эмиссионной спектроскопии тлеющего разряда и спектроскопии комбинационного рассеяния света. Механические и трибологические свойства покрытий определены с помощью методов наноиндентирования, скратч-тестирования и трибологических испытаний. Исследована жаростойкость покрытий в диапазоне температур 1200–1600 °С. Установлено, что покрытия оптимального состава обладают твердостью 20 ГПа, модулем упругости 210 ГПа, упругим восстановлением 53 %, коэффициентом трения 0,6 в паре с твердосплавным шариком, а также жаростойкостью выше 1200 °С, что обусловлено формированием на их поверхности защитной пленки на основе SiO2. Покрытия, осажденные из мишени состава Si70B25C5 в среде Ar+15%N2, помимо высокой жаростойкости при t = 1200 °С и выдержке в течение 12 ч показали стойкость к кратковременным тепловым нагрузкам при температурах 1400, 1500 и 1600 °С