Том 43, № 10 (2017)
- Жылы: 2017
- Мақалалар: 23
- URL: https://journals.rcsi.science/1063-7850/issue/view/12794
Article
Anti-scratch AlMgB14 Gorilla® Glass coating
Аннотация
Hard aluminum–magnesium boride (BAM) films were fabricated onto Corning® Gorilla® Glass by radio-frequency magnetron sputtering of a single stoichiometric AlMgB14 target. BAM films exhibit a Vickers hardness from 10 to 30 GPa and a Young’s modulus from 80 to 160 GPa depending on applied loading forces. Deposited hard coating increases the critical load at which glass substrate cracks. The adhesion energy of BAM films on Gorilla® Glass is 6.4 J/m2.
The physical mechanism of the deviation of cathode thermionic emission from the Schottky law
Аннотация
The deviation of the I–V characteristics of cathode materials in microwave devices from the Schottky law is caused by the occurrence of drift and diffusion of oxygen vacancies in barium-oxide crystallites, which are emission-active components of the cathode materials. The processing of experimental dependences using the proposed mathematical tools makes it possible to determine the barium-oxide-crystallite thickness and diffusivity of oxygen vacancies. The known diffusivity allows determining the presence of microimpurities in barium oxide, which affect its emission properties.
Influence of the surface ligand molecules length on the optical properties and photoconductivity of PbS quantum dot condensates
Аннотация
The influence of ligands—organic molecules on the quantum dot (QD) surface—on the optical properties of thin-layer condensates of lead sulfide QDs and the photoconductivity of diode structures based on them has been investigated. A decrease in the ligand length by a factor of 4 is shown to reduce significantly the luminescence-decay time and increase exponentially the conductivity.
Magnetization of superconducting rings by long-duration pulses
Аннотация
After pulsed magnetization of the rings of high-temperature superconductors with a rectangular cross section, the magnitude of the trapped field has been measured depending on the decay time of the magnetization field. It has been shown that, by making use of the break of shielding current, one can magnetize the ring with a single pulse the rings to the maximum value corresponding to the field cooling process.
A spherical distributed Bragg reflector based on a-Si1–xCx: H and a-SiO2 layers
Аннотация
A spherical distributed Bragg reflector (SDBR) for near-infrared applications is elaborated via plasma-enhanced chemical-vapor deposition. It consists of the alternating quarter-wave layers of amorphous hydrogenized silicon carbide (a-Si1–xCx: H) and amorphous silicon oxide (a-SiO2) deposited onto a glass microsphere. The reflection spectra of the SDBR are measured at different points of its surface. In all cases, the Bragg-reflection bands, as well as the wavelength range of their overlap, are detected, evidencing the presence of a complete photonic band gap in the SDBR obtained.
Comparison of flash-memory elements using materials based on graphene
Аннотация
Charge capture on flash-memory test structures with floating gates made of graphene (few-layer graphene) and its compounds (graphene oxide and partially fluorinated graphene) is investigated. A comparison of the memory window for different structures has shown the potential of using reduced graphene oxide, graphene with only a few layers, and fluorographene. For the first time, partially fluorinated graphene has been employed as a floating gate in flash-memory structures. Graphene-based materials are promising for 2D printing technologies and flexible electronics.
Self-similarity of the desynchronization process in a network of generalized Kuramoto oscillators
Аннотация
The phenomenon of explosive synchronization in a network of generalized Kuramoto oscillators is considered. It has been shown that this process results from self-similarity observed after the loss of stability by synchronous clusters of different dimensions. The appearance of self-similarity can be revealed when studying the processes of destruction in the synchronous state of a network. It has been demonstrated that a system passes through a sequence of self-similar configurations of interacting oscillators after the abrupt destruction of a synchronous regime.
Initiation of explosive conversions in energy-saturated nanoporous silicon-based compounds with fast semiconductor switches and energy-releasing elements
Аннотация
The first findings concerning the initiation of explosive conversions in energy-saturated nanoporous silicon-based compounds via the electrical explosion of a semiconductor bridge are presented. The obtained results indicate that the energy parameters of an explosive conversion depend on the mass of a combustible agent—namely, nanoporous silicon—and the silicon-doping type.
Electric thermal inspection of metal sheets
Аннотация
An electrothermal method of nondestructive inspection of conducting materials is proposed and tested experimentally. This method is based on filming the IR emission of the surface induced in a sheet sample excited by a millisecond current pulse. Subsequent computer processing of the nonstationary thermalfield patterns reveals millimeter and submillimeter defects and provides an opportunity to estimate their geometrical parameters and the temperature-diffusivity coefficient of the material.
The detection of low concentrations of water molecules in plasma by methods of actinometry and simulation
Аннотация
Correlations of H2O molecules and atoms of hydrogen concentrations in plasma of humid inert gases are studied. The observed data of water-vapor concentration are compared to the results of simulation of a plasma-chemical process. The scaling of the results is discussed.
A study of transition regions in InAsPSb/InAs heterostructures grown by MOVPE
Аннотация
A study by secondary-ion mass spectrometry of InAsxPySb1–x–y/InAs heterostructures (x > 0.55) grown by vapor-phase epitaxy for lattice-mismatched with substrates samples revealed a noticeable and extended (~800 nm) exponential variation of the As and P content (y up to 0.12) across the layer thickness. The lattice mismatch calculated from the experimentally determined distribution of the As and P components was the strongest at the interface between the epitaxial layer and the substrate and decreased away from the heterointerface into the epitaxial layer.
Precision calibration of the silicon doping level in gallium arsenide epitaxial layers
Аннотация
An approach to precision calibration of the silicon doping level in gallium arsenide epitaxial layers is discussed that is based on studying the dependence of the carrier density in the test GaAs layer on the silicon- source temperature using the Hall-effect and CV profiling techniques. The parameters are measured by standard or certified measuring techniques and approved measuring instruments. It is demonstrated that the use of CV profiling for controlling the carrier density in the test GaAs layer at the thorough optimization of the measuring procedure ensures the highest accuracy and reliability of doping level calibration in the epitaxial layers with a relative error of no larger than 2.5%.
A study of the effect of random dopant-concentration fluctuations on current in semiconductor superlattices
Аннотация
The influence exerted by random dopant-concentration fluctuations on the current–voltage characteristics of the current flowing through a semiconductor superlattice has been studied. It was shown that the characteristics of the current flowing through the superlattice noticeably vary with the amplitude of fluctuations of nanostructure parameters. It was possible to find for a small sample the probability-density distribution of the integrated absolute values of the difference of currents at various amplitudes of the dopantconcentration fluctuations.
The effect of temperature of a cone nose-tip on the spectra of disturbances in the hypersound boundary layer
Аннотация
The results of an experimental study of the influence of local heating/cooling of a blunted cone nose-tip on the development of perturbations in the boundary layer for Mach number M = 6 are presented. A comparative analysis of the pressure-pulsation spectra on the cone surface has been carried out. It is shown that heating/cooling in the boundary layer of an acute cone leads to destabilization/stabilization of the perturbations of the second mode. For blunted cones, the opposite effect has been observed: heating leads to weak stabilization of disturbances, and cooling leads to destabilization. This effect is enhanced by increasing the bluntness radius of the cone nose-tip.
Generation of microwave oscillations in a superconducting tunnel mesa-structure with a ferromagnetic insulator interlayer
Аннотация
Spin-polarized current in thin-film tunnel mesa-structures formed by epitaxial cuprate superconducting (YBa2Cu3O7–δ) and manganite (LaMnO3) films and an upper superconducting Au–Nb bilayer is studied experimentally. Intrinsic narrow-band generation in the microwave range is reported. Its frequency is tuned by the bias voltage and an external magnetic field.
Application of a new model of residual magnetization of iron for calculating the deflecting magnet of an accelerator
Аннотация
Allowing for residual magnetization of iron is necessary when calculating the magnetic field of elements of electron-optical channels in charged-particle accelerators because the contribution of residual magnetization to the field in the gap can be on the order of mT. Moreover, the magnitude and sign of this contribution depend on the magnetization process. Earlier, we proposed a model of residual magnetization of iron with the use of a small number of magnetic domain types. Here, an algorithm for magnetic-field calculation with the use of this model is described. The ability of the algorithm was demonstrated for the case of a simplest electromagnet with an O-shaped magnetic circuit. Comparison with the measurement results demonstrated a satisfactory accuracy of allowing for residual magnetization.
Switching of 100-kV pulses in a planar “open” discharge with generation of counterpropagating electron beams
Аннотация
Some results of studying a planar “open” discharge with generation of counterpropagating electron beams at high voltages and appreciable working gas pressures up to atmospheric one are presented. The possibility of its functioning in helium at a voltage above 100 kV is demonstrated, and an increase in the working voltage does not prevent fast breakdown with characteristic switching times of ~1 ns. A specific feature of this type of discharge is the existence of a gas-pressure region, where the discharge-development delay time nonmonotonically depends on the voltage due to the competition between emission processes leading to breakdown.
Determination of the refractive index of dehydrated cells by means of digital holographic microscopy
Аннотация
Spatial distributions of the integral refractive index in dehydrated cells of human oral cavity epithelium are obtained by means of digital holographic microscopy, and mean refractive index of the cells is determined. The statistical analysis of the data obtained is carried out, and absolute errors of the method are estimated for different experimental conditions.
Dynamics of cathode spots in an axial magnetic field on the fall of a current pulse in a high-current vacuum arc
Аннотация
The cathode attachment of a high-current vacuum arc on the fall of a current pulse was studied. Contacts generating an axial magnetic field were used. The revealed transformation of the attachment shape near zero current was explained quantitatively in a way that was in satisfactory agreement with experimental results.
The effect of thermal cycling on the martensitic transformations of (TiNiMoFe)Ag alloys
Аннотация
The effect of composition and thermal cycling on the phase transformations of multicomponent (TiNiMoFe)Ag alloys with a silver concentration of up to 1.5 at % is studied. Based on the temperature dependence of the electrical resistivity of the alloys under study, the characteristic temperatures are determined and a diagram of martensitic transformations is plotted. A correlation between the characteristic temperatures of the martensitic transformations and the structural-phase states of the (TiNiMoFe)Ag alloys is revealed.
Internal density waves of shock type induced by chemoconvection in miscible reacting liquids
Аннотация
A theoretical explanation of the phenomenon of spontaneous emergence of density waves experimentally observed recently in bilayered systems of miscible liquids placed in a narrow vertical gap of the Hele–Shaw cell in the gravitational field is provided. Upper and lower layers represent aqueous solutions of acids and bases, respectively, whose contact leads to the beginning of a neutralization reaction. The process is accompanied by a strong dependence of the reagent’s diffusion coefficients on their concentrations, giving rise to the generation of local density pockets, in which convection develops. The cavities collapse under certain conditions, causing a density jump, which moves faster than typical perturbations in a medium and takes the form of a shock wave. A mathematical model of the phenomenon is proposed, which can be formally reduced to equations of motion of a compressible gas under certain assumptions. Numerical calculations are given and compared with the experimental data.
Model of an ion flow and a method for calculating the erosion of discharge-chamber walls in a stationary plasma thruster
Аннотация
Morozov’s stationary plasma thrusters (SPTs) are used effectively in motion-control systems of Russian and foreign spacecraft, and the field of their application is still expanding. For this reason, the demands placed in the output parameters and lifetime of such thrusters are becoming more stringent. When solving the problems of increasing the service lifetime of SPTs, methods for predicting the erosion of discharge-chamber walls–a process that limits the lifetime of a thruster—are useful. We developed one such method earlier, which has been efficiently used in the development of modern SPTs. This letter presents an additional physical grounding and further development of the main ideas of this method on the basis of results obtained in recent years. This grounding makes it possible to expand the range of applicability of the method.
Nanocrystalline α-Al2O3 coatings obtained by reactive thermal anodic evaporation in arc discharge at low temperature
Аннотация
Al2O3 nanocrystalline coatings are obtained for the first time by anodic thermal evaporation of aluminum in an arc discharge in an oxygen–argon mixture at a temperature of 600°C on stainless-steel substrates with a Cr2O3 sublayer. The effect of the surface state of the samples and ion energy on the phase composition, microstructure, and properties of the coating is assessed. The α-Al2O3 phase is formed in the range of the bias potential of 25–200 V, with the growth of which the microcrystallite size decreases from 60 to 15 nm and the hardness of the coating increases from 8 to 20 GPa.