Abstract The paper discusses the problem of computer simulation of explosive emission processes in strong electromagnetic fields. In this work, a numerical method for calculating electron emission ...from the surface of a metal cathode for the axial symmetric geometry of a technical system is proposed. For modelling, the particle method and grid calculations of electromagnetic fields based on Maxwell’s equations are applied. The approach uses the representation of large smoothed Gaussian particles and implements calculations of the electromagnetic fields on Cartesian spatial grids. The software realization is directed towards on parallel computing. The calculation of the emission process in a coaxial cylindrical diode with magnetic self-insulation with the use of developed technique was carried out. The process is considered for two situations: with and without the longitudinal plasma layer. The calculations show that the presence of plasma leads to an increase in the emission current. This result is consistent with the results of experiments.
The conditions of detonation synthesis of nanodiamonds do not affect the size of diamond microcrystallites too much, as was shown in numerous experimental studies. This is because microcrystallites ...are formed almost instantly at the moment of explosive detonation, when conditions are created for crystallization of the diamond carbon phase. Further expansion of detonation products only leads to the creation and enlargement of particle agglomerates. The product of detonation synthesis is always a powder consisting of agglomerates of carbon particles of diamond and non-diamond phases with impurities. The size, density and specific surface area of the agglomerates can be different depending on the synthesis conditions. These product characteristics are of great importance for further technological applications. Meanwhile, the processes of agglomerate formation under conditions of expansion of detonation products have not yet been considered. In this paper, we theoretically consider this process. The dependences of the size and specific surface of carbon agglomerates on the conditions of detonation synthesis were obtained, and comparison with experimental data was made.
Gallium monosulfide (GaS), a representative of Group III monochalcogenide layered materials, is a wide-bandgap semiconductor. It is considered an ideal material for light detectors in the blue and ...near ultraviolet ranges of the spectrum. In this work, for the first time, the method of plasma-enhanced chemical vapor deposition (PECVD) was applied to obtain thin GaS films on various substrates, where high-purity gallium and sulfur served as starting materials. To initiate the interaction between the reactants, a nonequilibrium RF discharge (40.68 MHz) plasma at a pressure of 0.1 torr was used. The influence of the substrate nature on the stoichiometry, structure, and surface morphology of GaS films has been studied. The plasma-chemical process was monitored using optical emission spectroscopy.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A process for fabricating Zn-doped (up to 10 at %) β-Ga
2
O
3
thin films by plasma-enhanced chemical vapor deposition has been studied. High-purity gallium, zinc, and oxygen were used as starting ...materials, and hydrogen was chosen as the carrier and plasma gas. A low-temperature nonequilibrium RF (40.68 MHz) discharge plasma at a reduced pressure (0.01 torr) was used to initiate chemical reactions of precursors. The plasma-chemical process was monitored using optical emission spectroscopy. Structural properties and morphology of the deposited β-Ga
2
O
3
films were studied by various methods.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Geochronological studies of volcanic rocks ascribed to the Late Mesozoic Eastern Mongolian Volcanic Belt (EMVB) allowed the recognition of several groups, which differ in age and composition of ...igneous associations, as well as their occurrence. The youngest group (~215 Ma) includes the rocks of bimodal association abundant in the western part of the EMVB. The next group (170–150 Ma) mostly consists of felsic lavas of the shoshonite–latite association composing the large volcanic fields in the eastern part of the EMVB. The rocks with the age of 140–105 Ma form a cover of the EMVB and mostly include basaltic trachyandesite, the fields of which are accompanied by small volcanoes of trachydacite and trachyrhyolite. Separated extrusions of alkaline basaltoids formed in age range of 105–80 Ma. The rock associations of various ages have different geological links with ambient igneous complexes. By age and composition, the Late Triassic bimodal complex is compared with similar associations that occur in Central Mongolia and West Transbaikalia along the frame of the Khentei–Dauria batholith. Their origination is related to the formation of the Early Mesozoic Khentei–Dauria zoned igneous area. The Middle to Late Jurassic igneous complexes are mostly localized in the eastern part of the EMVB. Their fields occur within the area of Late Jurassic volcanic fields of the Great Xing’an Volcanic Belt (GXVB), which are similar both in the age of the formation and in the composition of volcanic associations. The Cretaceous magmatism was responsible for the main evolution of the EMVB, which was accompanied by rifting and formation of numerous troughs and grabens, as well as regular evolution of its mantle sources directed toward the increasing amount of an intraplate component. The sizes, boundaries, and characteristics of the EMVB magmatism are refined. Its western boundary is shifted to the east and is determined by a frontal NW-trending fault system, which controls a chain of Early Cretaceous granitic plutons, as well as rocks of the Late Mesozoic extrusive complex. The eastern boundary of the area is shifted to the west, where it coincides with a field of the Early Cretaceous extrusive complex. Taking into account data on the alien setting of the Late Triassic and Middle to Late Jurassic complexes in the EMVB structure, it is established that the EMVB igneous products mainly include mafic volcanic rocks. This is in agreement with similarity of the EMVB and other Late Mesozoic volcanic areas of the intracontinental part of East Asia, with a subordinate role of felsic igneous rocks.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Gallium selenide (GaSe) thin films on silicon(111) have been first grown by plasma-enhanced chemical vapor deposition (PECVD) using high-purity elemental gallium and selenium as the precursors. The ...reactive plasma components formed in the gas phase have been studied by optical emission spectroscopy. All grown films have a stoichiometry similar to that of GaSe. An increase in the plasma discharge power to 50 W and higher leads to the formation of an ε-GaSe phase, an improvement in the structural quality of the films, and an increase in the grain sizes with simultaneous grain compaction.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The age and geochemical characteristics of alkaline rocks of the Dugda massif (Eastern Tuva), attributed to the East Sayan Late Paleozoic rare-metal magmatic zone, have been determined. The massif is ...composed of nepheline syenites, which dominate over alkaline quartz syenites and alkaline granites. The age of the rocks has been estimated by the
40
Ar/
39
Ar method for amphibole and the U–Pb SIMS method for zircon. The age of the rocks was 291 ± 5 Ma for nepheline syenites, 284 ± 2 Ma for alkaline quartz syenites, and 285 ± 4 Ma and 287 ± 1 Ma for alkaline granites. These estimations make it possible to determine the age of the massif with an average value of ~287 Ma. Rocks with different compositions are characterized by close geochemical characteristics. They are enriched in the majority of incompatible elements in comparison with the average composition of the Earth’s crust and are characterized by multi-element spectra similar to A-type granitoids. Variations in the contents of the incompatible elements in the rocks of the massif exceed two orders of magnitude and reach ore concentrations (Zr up to 2.5 wt %, Nb up to 0.2 wt %, Ta up to 250 ppm, and Y up to 0.2 wt %). The geological position of the massif and specific features of the composition of its rocks, allowed us, firstly, to clarify the relationship between the East Sayan Late Paleozoic rare-metal zone and the fault system, which defines the western boundary of the Tuva–Mongolian microcontinent; secondly, to limit the time of alkaline magmatism to the interval of 309–285 Ma; and thirdly, to conclude that the spectrum of rare-metal igneous rocks of the zone is not limited to alkaline granitoids, but also includes alkaline nepheline syenites.
The Udokan volcanic plateau differs from other volcanic regions of the Late Cenozoic volcanic province of East Asia in the high alkalinity of volcanic rocks, their potassium specialization, and rock ...composition, varying from melaleucytitis and melanephelinites to alkaline trachytes. The presence of alkaline-salic rocks in volcanic associations makes it unique to the province. The reasons that determined the unique magmatism of the Udokan plateau are considered. The data of geochemical and isotopic studies have shown that the moderately enriched magma of the mantle plume served as a melt source in the region. The initial melts were formed under conditions of garnet stability at low degrees of melting. This contributed to their enrichment in alkalis and other incompatible elements that is especially characteristic of ultramafic rocks. It is established that fractionation processes controlled the distribution of the trace elements in the rocks of volcanic associations. Deep differentiation of the magmas to alkaline trachytes occurred in the peripheral magma chambers. Here, magmas interacted with intracrustal waters, which led to a change in their oxygen isotopic composition. It is shown that contamination did not play a decisive role in the formation of lava plateau rocks.
The possibilities of the synthesis of new derivatives of quinazolin-4(3
H
)-ones by the reactions of different functionalized anthranilic acids with imino ether generated
in situ
from ...2-cyanopyrimidine were studied. It was shown that the presence of different substituents in the anthranilic acids, including halogen atoms, methoxy and methyl groups, did not interfere with the reaction.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
—The Late Mesozoic volcanic province of East Asia is considered in relation to global geological events. The main structure-forming events and largest magmatic productivity of the province coincided ...with the peak of widely manifested plume activity in the Early Cretaceous. A geodynamic model of magmatic province formation of is proposed, relating the development of the province to the complex geodynamic setting for the interaction of the convergent boundary with the hot mantle field. The Pacific marginal magmatic belt formed in the front zone of convergence, where accretion of terranes occurred with prevalent supersubduction magma-forming mechanisms. In the western part of the province outside convergence zone an intraplate volcanic areas formed due to the activity of small mantle plumes.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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