Comparative Characteristics of Stress and Structure of TiN and Ti0.5-xAl0.5YxN Coatings Prepared by Filtered Vacuum-Arc PIIID Method

A comparative study of the structure and stress state of Ti0.5-xAl0.5YxN and TiN coatings deposited under identical conditions from the filtered vacuum-arc plasma under high voltage pulsed bias potential on the substrate was carried out. It was found that for Ti0.5Al0.5N coatings the dependence of the residual stress on the amplitude of the pulsed voltage potential is non-monotonic with a minimum when the amplitude is of 1 kV. As for TiN films, a monotonic decrease in the level of residual stresses takes place when the amplitude of the potential is increased in the range 0-2.5 kV. Non-monotonic dependence for multicomponent coatings Ti-Al-Y-N may occur due to the possibility of phase transition associated with the decay of the supersaturated solid solution (Ti,Al)N stimulated by high energy ion bombardment. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3491

Water masers in dusty environments

We study in details a pumping mechanism for the lambda=1.35 cm maser transition 6_16 -> 5_23 in ortho-water based on the difference between gas and dust temperatures. The upper maser level is populated radiatively through 4_14 -> 5_05 and 5_05 -> 6_16 transitions. The heat sink is realized by absorbing the 45 mum photons, corresponding to the 5_23 -> 4_14 transition, by cold dust. We compute the inversion of maser level populations in the optically thick medium as a function of the hydrogen concentration, the gas-to-dust mass ratio, and the difference between the gas and the dust temperatures. The main results of numerical simulations are interpreted in terms of a simplified four-level model. We show that the maser strength depends mostly on the product of hydrogen concentration and the dust-to-water mass ratio but not on the size distribution of the dust particles or their type. We also suggest approximate formulae that describe accurately the inversion and can be used for fast calculations of the maser luminosity. Depending on the gas temperature, the maximum maser luminosity is reached when the water concentration N_water ~ 10^6-10^7 cm^-3 times the dust-to-hydrogen mass ratio, and the inversion completely disappears at density just an order of magnitude larger. For the dust temperature of 130 K, the 6_16 -> 5_23 transition becomes inverted already at the temperature difference of Delta T ~1 K, while other possible masing transitions require a larger Delta T > 30 K. We identify the region of the parameter space where other ortho- and para-water masing transitions can appear.Comment: 14 pages, 10 figures; submitted to A&

Intrinsic stress formation in multi-component coatings produced by plasma ion deposition in modes of DC and pulse bias potentials

In the model of nonlocal thermoelastic peak of low-energy ion a formula for intrinsic stress in multi-component material deposited from mixed beam of differently charged ions in modes of DC and pulse bias potentials is derived. Calculation of intrinsic stress σ depending on bias potential U in coating Cr-Al-N deposited from mixed ion beam Cr(50%)Al(50%) is executed at different modes and substrate temperatures T₀. It is shown that maximum of σ(U) in pulse bias potential mode shifts towards higher U as compared with DC mode whereas increase of T₀ leads to opposite effect.У рамках моделі нелокального термопружного піка низькоенергетичного іона отримана формула для внутрішніх напружень у багатокомпонентному матеріалі, що осаджується зі змішаного пучка різнозаряджених іонів у режимах постійного й імпульсного потенціалів. Проведено розрахунок залежності внутрішніх напружень σ від потенціалу зміщення U у покритті Cr-Al-N, що осаджується зі змішаного потоку Cr(50%)Al(50%) іонів при різних режимах і температурах осадження T₀. Показано. що в режимі імпульсного потенціалу максимум кривої σ(U) зміщується у бік більших значень U, у порівнянні з режимом постійного потенціалу. Підвищення T₀ веде до зворотного ефекту.В рамках модели нелокального термоупругого пика низкоэнергетического иона получена формула для внутренних напряжений в многокомпонентном материале, осаждаемом из смешанного пучка разнозаряженных ионов в режимах постоянного и импульсного потенциалов. Проведен расчет зависимости внутренних напряжений σ от потенциала смещения U в покрытии Cr-Al-N, осаждаемом из смешанного потока Cr(50%)Al(50%) ионов при различных режимах и температурах осаждения T₀. Показано, что в режиме импульсного потенциала максимум кривой σ(U) смещается в сторону больших значений U, по сравнению с режимом постоянного потенциала. Повышение T₀ ведет к обратному эффекту

Optimization of the magnetic system of a vacuum-arc plasma source with a straight line filter

The vacuum-arc plasma source with a rectilinear filter has been optimized for deposition of coatings on large size products. The calculations of the magnetic configuration options of the system were performed by using the FEMM program. New design of the output coil of the filter allows increase by 1.3 times the efficiency of plasma transportation to the substrate with a diameter of 300 mm. Plasma instabilities are proposed for the explanation the features of the motion of vacuum-arc plasma through the regions of an inhomogeneous magnetic field in a rectilinear macroparticles filter with a “magnetic island”.Проведено оптимізацію вакуумно-дугового джерела плазми з прямолінійним фільтром для нанесення покриттів на великогабаритні вироби. Розрахунки варіантів магнітної конфігурації системи проводилися з використанням програми FEMM. Нова конструкція вихідної котушки фільтра дозволяє в 1,3 разa збільшити ефективність транспортування плазми до підкладки діаметром 300 мм. Особливості руху вакуумно-дугової плазми в прямолінійному фільтрі макрочасток з “магнітним островом” пояснюються розвитком плазмових нестійкостей в областях неоднорідного магнітного поля.Вакуумно-дуговой источник плазмы с прямолинейным фильтром оптимизирован для нанесения покрытий на крупногабаритные изделия. Расчеты вариантов магнитной конфигурации системы проводились с использованием программы FEMM. Новая конструкция выходной катушки фильтра позволяет в 1,3 раза увеличить эффективность транспортировки плазмы к подложке диаметром 300 мм. Особенности движения вакуумно-дуговой плазмы в прямолинейном фильтре макрочастиц с “магнитным островом” объясняются развитием плазменных неустойчивостей в областях неоднородного магнитного поля

First Interferometric Images of the 36 GHz Methanol Masers in the DR21 Complex

Class I methanol masers are believed to be produced in the shock-excited environment around star-forming regions. Many authors have argued that the appearance of various subsets of class I masers may be indicative of specific evolutionary stages of star formation or excitation conditions. Until recently, however, no major interferometer was capable of imaging the important 36 GHz transition. We report on Expanded Very Large Array observations of the 36 GHz methanol masers and Submillimeter Array observations of the 229 GHz methanol masers in DR21(OH), DR21N, and DR21W. The distribution of 36 GHz masers in the outflow of DR21(OH) is similar to that of the other class I methanol transitions, with numerous multitransition spatial overlaps. At the site of the main continuum source in DR21(OH), class I masers at 36 and 229 GHz are found in virtual overlap with class II 6.7 GHz masers. To the south of the outflow, the 36 GHz masers are scattered over a large region but usually do not appear coincident with 44 GHz masers. In DR21W we detect an "S-curve" signature in Stokes V that implies a large value of the magnetic field strength if interpreted as due to Zeeman splitting, suggesting either that class I masers may exist at higher densities than previously believed or that the direct Zeeman interpretation of S-curve Stokes V profiles in class I masers may be incorrect. We find a diverse variety of different maser phenomena in these sources, suggestive of differing physical conditions among them.Comment: 8 pages, accepted for publication in Ap

A self-consistent model of a 22 GHz water maser in a dusty environment near late-type stars

We study the conditions for operation of the 22 GHz ortho-water maser in a dusty medium near late-type stars. The main physical processes, such as exchange of energy between dust and gas in the radiation field of a star, radiative cooling by water molecules and pumping of water masers are described self-consistently. We show that the presence of dust grains of various types (or of one type with size distribution) strongly affects the maser action. The pumping mechanism based on the presence of the dust of different optical properties is able to explain water masers in the silicate carbon star V778 Cyg. However, the masers in the winds from asymptotic giant branch stars require an additional source of heating, for instance due to the dust drift through the gas.Comment: 15 pages, 15 figures, A&A, in pres

Dense Gas and Star Formation: Characteristics of Cloud Cores Associated with Water Masers

We have observed 150 regions of massive star formation, selected originally by the presence of a water maser, in the J = 5-4, 3-2, and 2-1 transitions of CS, and 49 regions in the same transitions of C$^{34}$S. Over 90% of the 150 regions were detected in the J = 2-1 and 3-2 transitions of CS and 75% were detected in the J=5-4 transition. We have combined the data with the J = 7-6 data from our original survey (Plume et al. 1992) to determine the density by analyzing the excitation of the rotational levels. Using Large Velocity Gradient (LVG) models, we have determined densities and column densities for 71 of these regions. The gas densities are very high (the mean log of the density is 5.9), but much less than the critical density of the J=7-6 line. Small maps of 25 of the sources in the J = 5-4 line yield a mean diameter of 1.0 pc. The mean virial mass is 3800 solar masses. The mean ratio of bolometric luminosity to virial mass (L/M) is 190, about 50 times higher than estimates using CO emission, suggesting that star formation is much more efficient in the dense gas probed in this study. The gas depletion time for the dense gas is roughly 1.3 x 10^7 yr. We find no statistically significant linewidth--size or density--size relationships in our data. Instead, both linewidth and density are larger for a given size than would be predicted by the usual relationships. We find that the linewidth increases with density, the opposite of what would be predicted by the usual arguments. We estimate that the luminosity of our Galaxy (excluding the inner 400 pc) in the CS J = 5-4 transition is 15 to 23 L_sun, considerably less than the luminosity in this line within the central 100 pc of NGC 253 and M82. In addition, the ratio of far-infrared luminosity to CS luminosity is higher in M82 than in any cloud in our sample.Comment: 26 pages, 6 postscript figures, 3 postscript tables. Uses AAS Latex macros, accepted for Astrophysical Journa

Surface nanorelief modification of constructional materials at low energy ion bombardment

Process of thermal smoothing at bombardment of metal surfaces by low energy heavy ions is investigated. It is shown, that smoothing can occur in nonlocal thermoelastic peak of ion under action of forces of surface tension at spreading the melted material on the surface. The model of thermal smoothing alternative to model of ion polishing due to ion sputtering of target atoms is developed. Criteria of applicability of model for any combination “ion–target”, and analytical expressions for basic parameters of process of smoothing (size of smoothing area created by single ion, time of smoothing) are received.Теоретично досліджувався процес теплового згладжування при бомбардуванні металевих поверхонь важкими іонами низьких енергій. Показано, що вирівнювання поверхні може відбуватися під дією сил поверхневого натягу при розтіканні уздовж поверхні розплавленого матеріалу, що утворюється в нелокальному тепловому піку іона. Розроблено модель теплового згладжування, яка альтернативна моделі іонного полірування за рахунок розпилення іонів мішені. Отримано критерії, що визначають застосовність моделі для довільної комбінації «іон-мішень», і аналітичні вирази для основних параметрів процесу згладжування (розмір області згладжування, яка створювана одиночним іоном, час згладжування).Теоретически исследовался процесс теплового сглаживания при бомбардировке поверхности металлов тяжелыми ионами низкой энергии. Показано, что выравнивание поверхности может происходить под действием сил поверхностного натяжения при растекании вдоль поверхности расплавленного материала, образующегося в нелокальном тепловом пике. Разработана модель теплового сглаживания, альтернативная модели ионной полировки, за счет ионного распыления. Получены критерии, определяющие применимость модели для произвольной комбинации «ион-мишень», а также аналитические выражения для основных параметров процесса сглаживания (размер области сглаживания, создаваемой одиночным ионом, время сглаживания)