a brief description of the principles of functioning of the device creating high intensity acoustic fields in presented. The processes of forming the cavitation bubbles are explained, and also a reasons, why the cavitationg liquid might be considered as a separate medium. The article contains the results of experimental researches about the energy dissipation in a complicated way. The researches about spectral characteristics were held, proving the existence of the new radiating medium.
A comparative study of the wear resistance, hardness and modulus of elasticity of ENAW-2024 aluminum alloy samples with and without a mineral coating was carried out. The wear resistance of the samples was studied by the method of multi-cycle friction, which makes it possible to measure the physicomechanical properties of thin modified material layers at the nanoscale. After the modification of the sample surface, the surface hardness and elastic modulus decreased by 20–36% and by 22–38%, respectively. At the same time, the wear resistance of the surface of the sample, modified by minerals, increased by more than 12 times compared with the wear resistance of the surface without modification. The parameters of the modified surface of the aluminum alloy, measured by sclerometry, can be further used to construct models of the surface modified by ultrafine mineral particles and to calculate the processes of friction and wear.
The work investigates some tribological parameters of the surfaces of friction pairs made of steel, with mineral layers. A comparative study of the friction coefficient of 18CrNiMo7-6 steel specimens with and without a mineral coating is performed. The lowest friction coefficient value was achieved for samples with mineral coating, without HFC hard surfacing before creating a mineral layer, and it was approximately 15% lower in comparison with the samples with HFC hard surfacing, but without mineral coating. The friction coefficient in the temperature range of 30…140 0С, with constant displacement speed of samples with mineral coatings is practically unchanged for every sample type, the variation range does not exceed 0.02, as contrasted with the friction coefficient of the samples with hard surfacing, but without mineral coating. The value of the coefficient of volumetric wear of an aluminum oxide toroid during rotation with disks with some types of mineral coatings was at the level of detection limit (less than 1.2x10-9 mm3/Nm), which is significantly less than the coefficient of volume wear of a toroid during rotation with disks without coating (4-7)х10-8 mm3/Nm.
The paper presents model of processes of charge state changing of gate dielectric of MIS structure under conditions of simultaneous influence of radiation and high-field injection of electrons. The model takes into account the generation of positive charge by both radiation and high-field ionization and, besides, it takes into consideration the interaction of injected electrons with charges taken place in the dielectric film because of concurrent influence by ionizing radiation and high fields. We model an influence of radiation on charge state of the dielectric films of MIS structures in a wide range of influences by radiation and high-field injection of electrons. We study an influence of electric field strength and intensity of radiation on processes of generation and annihilation of positive charge accumulated in the gate dielectric because of both radiation and high-field ionization. We make suggestions on use of radiation MIS sensors which are utilized under conditions of high-field injection of electrons into the gate dielectric.
The effect of isotopic modification of diamond lattice on photoluminescence (PL) and optical absorption spectra of ensembles of SiV− centers was studied. Thin epitaxial diamond layers were grown by a microwave plasma CH4/H2 mixtures using methane enriched to 99.96% for either 12C or 13C isotopes, while the Si doping was performed by adding a small percentage of silane SiH4 into the plasma. Temperature dependent SiV−ZPL spectra in absorption were measured at 3–80 K to monitor the evolution of the ZPL fine structure. It is found that the SiV− ZPL at 736.9 nm observed in PL for 12C diamond at T = 5 K, exhibits a blue shift of 1.78 meV, to 736.1 nm in 13C diamond matrix. Narrow ZPL with the width (FWHM) of 0.09 meV (21 GHz) was measured in absorption spectra at T = 3–30 K in the Si‐doped 13C diamond. Besides the charged SiV− center, the absorption of the neutral SiV0 defect at 946 nm wavelength has also been detected. From changes observed in SiV− phonon band structure in PL with isotopic modification, the band at 64 meV was confirmed to be a local vibration mode (LVM) involving a Si atom.
Apart from the main plasmon-polariton resonance of the surface-enhanced Raman scattering (SERS) occurring at 480 - 530 nm, an additional resonance was observed for substrates with two silver layers separated by a dielectric layer which support extra plasmon modes with decreased group velocities. The novel SERS resonance is shifted towards lower energies and has comparable amplitude,its exact energy position being determined by the thickness of the dielectric interlayer. The experimental findings provide a ground for the engineering of SERS-substrates with the spectral position of the additional resonance matched with the photon energy of the pump laser over a fairly wide range of laser wavelengths.
Single NV centers in HPHT IIa diamond are fabricated by helium implantation through lithographic masks. The concentrations of created NV centers in different growth sectors of HPHT are compared quantitatively. It is shown that the purest f001g growth sector (GS) of HPHT diamond allows to create groups of single NV centers in predetermined locations. The f001g GS HPHT diamond is thus considered a good material for applications that involve single NV centers.
We present the results of temperature- and polarization-dependent high-resolution optical spectroscopy studies of DyFe3(BO3)4 performed in spectral ranges 40-300cm-1 and 3000-23000cm-1. The crystal-field (CF) parameters for the Dy3+ ions in the P3121 (P3221) phase of DyFe3(BO3)4 are obtained from calculations based on the analysis of the measured f-f transitions. Recently, quadrupole helix chirality and its domain structure was observed in resonant x-ray diffraction experiments on DyFe3(BO3)4 using circularly polarized x rays [T. Usui, Y. Tanaka, H. Nakajima, M. Taguchi, A. Chainani, M. Oura, S. Shin, N. Katayama, H. Sawa, Y. Wakabayashi, and T. Kimura, Nat. Mater. 13, 611 (2014)10.1038/nmat3942]. Using the obtained set of the CF parameters, we calculate temperature dependencies of the electronic quadrupole moments of the Dy3+ ions induced by the low-symmetry (C2) CF component and show that the quadrupole helix chirality can be explained quantitatively. We also consider the temperature dependencies of the bulk magnetic dc-susceptibility and the helix chirality of the single-site magnetic susceptibility tensors of the Dy3+ ions in the paramagnetic P3121 (P3221) phase and suggest the neutron and resonant x-ray diffraction experiments in a magnetic field to reveal the helix chirality of field-induced magnetic moments.
The article describes the formulation and solution of the axisymmetric problem of quantify SSS composite cylinder with a sandy soil under the influence of an external load of plate foundations, analytical and numerical methods based on elastic-plastic properties of soils. Shown that the axial force on the composite cylinder is distributed between the sand-pile and the surrounding previously compacted weak soil in proportion to their stiffness and diameter ratio. It is noted that at a certain load in the sand pile, plastic deformations occur as a result of which the stresses are redistributed, and the total deformation of the composite cylinder develops nonlinearly. It is shown that, depending on the calculation model adopted in the sandy soil pile at stresses close to the ultimate value various forms of destruction forming, including the barrel at different levels. Stresses that this phenomenon was observed for the first time and requires further research and theoretical basis.
Changes in the morphology of the vanadium surface are studied as a result of the separate and sequential action of helium ions (for an energy of 30 keV, a dose of 1.0 × 1022 m–2, an ion-flux density of 4.8 × 1018 m–2 s –1, and a temperature of ~500 K) and high-power pulsed laser radiation in the Q-switched mode (power density of q = 1.2 × 1012 W/m2, pulse duration of τ0 = 50 ns, and a pulse number N varying from 1 to 4). It is found that the effect of laser irradiation on vanadium samples before and after ion implantation (resulting in the formation of a crater with a rim due to the splashing of melted metal) is identical. In the case of the preliminary introduction of helium into the material the splash of metal is more intense. Helium implanted into the samples causes radiation blistering; the subsequent influence of laser pulses intensifies material erosion in the area located immediately behind the rim (resulting in a growing number of peeled layers, merging blisters, etc.), which is probably triggered by high temperatures and thermal stresses emerging in this area (even after discontinuing laser irradiation). Under reactor operating conditions this effect can lead to increased plasma contamination. It is shown that the damage of a target inside the craters in the initial vanadium samples feature occasional cracks, wavy and droplet structures, as well as beading, whereas along with the above changes the samples pre-irradiated with helium contain no cracks inside the crater although areas showing boiling of the material are clearly visible.
Here we report targeted high-pressure synthesis of two novel high-TC hydride superconductors, P63/mmc-ThH9 and Fm3m-ThH10, with the experimental critical temperatures (TC) of 146 K and 159–161 K and upper critical magnetic fields 38 and 45 Tesla at pressures 170–175 Gigapascals, respectively. Superconductivity was evidenced by the observation of zero resistance and a decrease of TC under external magnetic field up to 16 Tesla. This is one of the highest critical temperatures that has been achieved experimentally in any compound, along with such materials as LaH10, H3S and HgBa2CaxCu2O6+z. Our experiments show that fcc-ThH10 has stabilization pressure of 85 GPa, making this material unique among all known high-TC metal polyhydrides. Two recently predicted Th-H compounds, I4/mmm-ThH4 (>86 GPa) and Cmc21-ThH6 (86–104 GPa), were also synthesized. Equations of state of obtained thorium polyhydrides were measured and found to be in excellent agreement with the theoretical calculations. New phases were examined theoretically and their electronic, phonon, and superconducting properties were calculated.
Professor Yuri E. Gorbatywas born 30 July 1932 in the city Grozny, in the Soviet Union. He has graduated from the Mendeleev Institute of Chemical Technology,Moscow, in 1955. He has got his Candidate of Sciences (Ph.D.) degree in 1963 for his work on “Non-equilibrium crystallization of the three-componentmelts”, and later in 1988 he was awarded a Doctor of Sciences degree for the work “The effect of temperature and pressure on the nearest ordering in liquid and supercritical water”. Between these two dates and then later in his scientific career Yuri E. Gorbaty has become one of the leading experts in the field of experimental studies of the structure and properties of fluids, especially aqueous fluids at high temperatures and pressures, by methods of IR and Raman spectroscopy and by X-ray diffraction.
Synthesis of bismuth complexes of etioporphyrin II, protoporphyrin IX dimethyl ester and three tetraphenylporphyrin derivatives in which iodine atom is an extraligand, was carried out. Obtained compounds were characterized by mass spectrometry, UV-vis, 1H NMR spectroscopy, and HPLC. The study of X-ray spectra showed that bismuth valence is +3. Bismuth atom coordinates four nitrogen atoms and one iodine atom. All four nitrogen atoms have equivalent binding energies. IR absorption spectra of free porphyrins bases and their bismuth complexes were studied. The comparison of IR absorption spectra of neat porphyrins shows no significant differences in vibrations of nitrogen-carbon cycles. As for bismuth complexes, vibrations bands of bismuth-iodine bonds ν(Bi-I) appear at 90–130 cm-1 in the long-wavelength spectra regions, as well as deformation vibrations involving bismuth, iodine and nitrogen atoms δ(NBiI) with frequencies 150–165 cm-1, deformation vibrations of δ[BiN4] pyramid at ~300 cm-1 and stretching vibrations bands of this complex fragment involving deformations of nitrogen-carbon ring, in the region of 335–375 cm-1. Quantum-chemical calculations were conducted including calculations of the vibrational spectra, dipole moments, and charge distribution on atoms (according to Mulliken). It was found that complex of bismuth iodide with etioporphyrin II is the most polar among the studied series compounds.
Two approaches for the synthesis of D-A chromophores containing arylhydrazonocyclopentadiene acceptor moieties were developed. The first approach includes the decarboxylative azo coupling reaction between penta(methoxycarbonyl)cyclopentadienyl potassium or sodium and aryldiazonium salts to give products containing four ester groups at the acceptor moiety. The second one includes the reaction of 1,3-dimethoxycarbonyl-4,5-diphenylcyclopentadienone with arylhydrazine hydrochlorides into arylhydrazonocyclopentadienes with two ester and two phenyl groups. Both series of compounds were investigated by means of absorption spectroscopy and the solvatochromic behavior of two representatives of each series was investigated in various dielectric environments. Both compounds demonstrated relative independence on the environment although the product with the stronger acceptor part was less stable and exhibited a slight hypsochromic shift in polar media. However, the optical properties of this product were strongly affected by the basicity of the medium due to the deprotonation of the NH-group. Quantum chemical modeling of the synthesized products adsorption spectra using different density functionals has shown that PBE0-D3/def2TZVP is an optimal method (out of three tested) for all compounds both in non-vibrationally-resolved and vibrationally-resolved TD-DFT calculations. Accounting for vibronic coupling in TD-DFT calculations is necessary to achieve good agreement with the experiment for compounds synthesized herein.
An approach to the synthesis of D-A chromophores containing hydrazinylidene cyclic acceptor moieties via the reaction of organolithium reagents with cyclic diazo compound precursors was developed. In contrast to conventional approaches the new one allows to introduce thiophene fragments into a chromophore molecule which is important for the better molecular planarity. The approach demonstrated convenience for the synthesis of hydrazinylidenecyclopentadiene, hydrazinylidenebarbituric and hydrazinylideneindanedione chromophores and a series of hydrazonocyclopentadienes with various aromatic and heterocyclic substituents were synthesized. The products demonstrated intense absorption of visible light with absorption maxima within 373–562 nm and extinction coefficients up to 36500 М−1⋅cm−1. Importantly, previously unavailable thiophenylhydrazones displayed longer wavelength absorption maxima and higher extinction coefficients relative to conventional arylhydrazones.
Superplastic Forming is an industrial process to produce thin-walled products of complex shape. At the same time this process allows one to obtain the products with close to uniform thickness distribution. The process exploits the abilities of some polycrystalline materials to large elongations before failure. The best formability can be achieved only under very specific conditions of temperature and strain rate. In order to calculate the pressure regime to sustain target strain rate in critical arias it is necessary to use finite element simulation. The pressure regime calculation lasts for a day’s especially while 3 dimensional elements are use. To reduce the time of calculation it is possible to use elements from membrane theory. The main idea of this approach is to use planar elements instead of tetrahedronal for 3D tasks or 2 nodes elements instead of triangular ones for axisymmetric tasks. This reduction doesn’t take in account share stress accruing into material. The main aim of this paper is to study the effect of elements type on the accuracy of thickness distribution prognosis.
Composite materials based on heterogeneous membranes MK-40 modified by a thin layer of homogeneous cation-exchange perfluorinated sulfo membrane MF-4SK doped with 2 and 5% ceria are prepared. The transport characteristics of these membranes in different ionic forms are studied. It is shown that the conductivity of ionic forms of membranes increases in the sequence Li+ < Na+ < К+ < H+. In all these forms except for the lithium form, the membrane containing 2% ceria has the highest conductivity. Modification leads to a considerable increase in selectivity of membranes which manifests itself as a decrease in transport numbers of anions (from 0.006 for the original membrane to 0.002 for the membrane with 5% ceria). The higher selectivity with respect to the transfer of nitrate ions as compared with chloride ions is observed.
We study the effect of periodic, spatially uniform temperature variation on mechanical properties and structural relaxation of amorphous alloys using molecular dynamics simulations. The disordered material is modeled via a non-additive binary mixture, which is annealed from the liquid to the glassy state with various cooling rates and then either aged at constant temperature or subjected to thermal treatment. We found that in comparison to aged samples, thermal cycling with respect to a reference temperature of approximately half the glass transition temperature leads to more relaxed states with lower levels of potential energy. The largest energy decrease was observed for rapidly quenched glasses cycled with the thermal amplitude slightly smaller than the reference temperature. Following the thermal treatment, the mechanical properties were probed via uniaxial tensile strain at the reference temperature and constant pressure. The numerical results indicate an inverse correlation between the levels of potential energy and values of the elastic modulus and yield stress as a function of the thermal amplitude.
The paper includes the description of the mathematical model, which simulates magnetic field distribution in the cathode area of the sputtering system discharge considering the current created by electrons moving along the surface of cathode-target. Presented results of the numerical modeling were received using the developed model. It is also shown that the current component, directed along the cathode surface significantly impacts total magnetic field distribution in the magnetron discharge.
The kinetics of growth of a nanosized germanium film deposited by magnetron sputtering on the Si(001) surface is studied using a developed experimental X-ray reflectometry technique distinguished by the joint recording of specularly reflected and diffusely scattered radiation. By using this technique, it is possible to perform in situ both the analysis of the morphology of the growing film and the control of its thickness with an accuracy to 1 nm. Dependences of the intensity of specular reflection, diffuse scattering, rate of growth, and mean square roughness and density of the film on the deposition time are obtained. According to the results of the measurement of specularly reflected radiation, the film roughness increases with time according to a power law. However, at a thickness of the film of 4 nm, a clearly defined maximum of diffuse scattering is observed, the angular position of which corresponds to the critical angle of total external reflection of germanium of 0.31°. This pattern of distribution of scattered radiation is explained by the manifestation of the Yoneda effect that consists in the anomalous X-ray scattering, the maximum of which corresponds to the critical angle θC of total external reflection from the film. It is established experimentally that, at the initial stage of growth, the film is formed by the Volmer–Weber mechanism. It is found using in situ X-ray reflectometry that the formation of a continuous layer of a germanium film occurs at its thickness of 7 nm; the subsequent growth of the film proceeds according to the power law σf ~ tβ, where β = 0.23.
Russia is one of the largest carbon emitters in the world, possessing huge resources of both fossil fuels and zero-carbon energy sources. The Paris Agreement targets require substantial efforts to limit global warming to “well below 2 °C”. Energy-economic modeling provides sound conclusions that continuation of existing energy and climate policy will lead to stabilization of energy carbon emissions in Russia at the current level in 2010–2050 (about 30% below 1990). Stronger mitigation policies could gradually reduce domestic energy CO2 emissions by 61% from 2010 to 2050 (75% below 1990). Deep decarbonization policies with even more ambitious commitments could ensure an 83% reduction in energy CO2 emissions from 2010 levels (88% below 1990) by 2050. All key sectors (energy, industries, transport, and buildings) can play a substantial role in decarbonizing the national economy. However Russia’s historical reliance on domestic consumption and exports of fossil fuels creates strong barriers to decarbonization. Emission reduction costs are expected to be below 29 USD/tCO2 by 2030, 55 USD/ tCO2 by 2040, and 82 USD/tCO2 by 2050 in the most ambitious decarbonization scenario. The results of this study provide insights into how Russia can enhance its ambitions to implement the Paris Agreement and contribute to global efforts toward building a climate-neutral economy by 2050.