Vol 64, No 7 (2019)

We consider the current state of a completely new area of science; microsystem electromechanics. Тhe wide spectra of its practical applications and prospects for further development are analyzed. We discuss in detail two main directions of creating micro- and nanoelectromechanical converters as basic elements of microsystem electromechanics: “top down” and “down top.” We also describe the main technological methods in constructing basic functional elements of microsystem electromechanics, areas of their application in traditional and new technologies (information and computer technologies, medicine, aerospace, rocket and artillery systems, etc.). At the same time, we discuss some key issues of generalized physical and mathematical modeling of microelectromechanical and nanoelectromechanical systems (MEMS and NEMS). A new generalized approach is proposed to study dynamic and energy characteristics of MEMS and NEMS as complex dynamic systems with binary conjugate subsystems. Based on proposed theoretical principles and models, the possibilities of studying electrophysical characteristics of biological nanostructures have been considered.

In this paper, we further develop the non-isothermal physicochemical model of reactive sputtering. A new version of the model describes the sputtering of a hot metal target in a mixture of argon and a reactive gas. The synthesis of the film on all surfaces of a vacuum chamber is specified as a surface chemical reaction. The basic postulate of chemical kinetics considering the Langmuir isotherm equation and the Arrhenius equation under non-isothermal conditions was used for mathematical description of the reaction. The dependence of target temperature on discharge current density is determined based on the measurement results of discharge spectra in the near-infrared range. A system of eight algebraic equations is proposed for the analytical description of the model. Using this system, the analysis of the effect of current density and reactive gas consumption on reactive sputtering of a hot titanium target in an argon + nitrogen mixture at a current density of 25–600 A/m² was performed. Warming up the target was established to shift the points of change in target operation modes to a region of lower nitrogen flow rates and reduce the hysteresis loop width as compared to a cold target. In this case, the effect of target evaporation on the process begins to occur at a current density of more than 400 A/m².

The surface flows of a liquid in the presence of a partially submerged vibrating plate are investigated. In the case of low-frequency plate vibrations, two vortices are formed on the surface of the liquid on each side of the plate in which liquid particles move away from plate surfaces. Under parametric excitation of transverse capillary waves near the boundary of the liquid layer wetting the plate surface, the flow direction in vortices becomes opposite. High-frequency vibrations of the plate create additional secondary vortices on the liquid surface.

We have measured the dynamic breakdown voltage in a long (80 cm) discharge tube in neon, argon, their mixture, and in argon with mercury vapor at pressures of 80–400 Pa in a wide range of anode voltage rise rates (dU/dt ~ 10^–4–10² kV/ms). We have detected a nonmonotonic dependence of the breakdown voltage on dU/dt with a minimum in the region 0.1–10 kV/ms. The breakdown voltage rise in the range of low voltage growth rate can probably be explained by the specific features of breakdown in long tubes and is associated with the accumulation of a surface charge on the tube walls. The charge reduces the potential difference between the anode and the wall and complicates the primary breakdown between them. The results of additional experiments with pulses superimposed on a constant bias voltage confirm the admissibility of such an explanation.

We report the results of investigation of elements of a rail-type electromagnetic accelerator (railgun), which are aimed at analysis of the mechanism of formation of a dense clean plasma jet with a high kinetic energy. The accelerator is tested with a pulsed gas puffing and with electrodes of different shapes and lengths, as well as an additional magnetic field produced by external current-carrying conductors. We have developed a method for monitoring plasma jet parameters on a plasma gun test bench using a pressure sensor and an infrared camera. We have analyzed the dependence of deuterium plasma jet pressure on the distance to the accelerator and estimated kinetic energy of the jet.

The destruction of homogeneous obstacles having different physical and mechanical properties is experimentally investigated under interaction with high-strength steel rams. The comparability of the results for different types of obstacles was ensured based on weight equivalency, that is, equality of the weight in the thickness for an area unit of the obstacle. The initial velocity of interaction was varied in the range 50–800 m/s. The double-exposed X-ray pulse recording was used to register ram motion after obstacle penetration. X-ray processing (i) gives the values of ram velocity behind the obstacle depending on its initial impact velocity and (ii) aids analyzing the features of obstacle destruction and their protecting properties by drawing penetration diagrams.

A concept of magnetic symmetry is used to show that centrosymmetric antiferromagnetic materials may exhibit linear flexomagnetic and flexoantiferromagnetic effects (magnetization induced by gradient of elastic stress or gradient of antiferromagnetic moment, respectively).

Magnetized and unmagnetized Co–Fe and Ni–Fe alloys fabricated on a two-high casting installation in the form of thin flexible amorphous films are promising materials for thermocouples. Using thin-film thermocouple arms, one can minimize temperature measurement errors due to heating by induction currents in a variable magnetic field.

It is shown that the shape of a sample determines the allowed lower-bound limit of the coercive force of material that can be used for fabrication of magnets with the given shape. Rings with radial magnetization are used as examples to show that such samples can be made of only rare-earth alloys with the coercive force that is sufficiently high to satisfy technical requirements at the maximum allowed working temperature of the magnet.

The C–V characteristic of the lateral source–substrate junction in a metal–nitride–oxide–semiconductor transistor has been simulated. With a certain voltage across the junction that depends on the dopant concentration in the substrate, a local trapped charge embedded in the nitride layer causes an anomalous rise or fall of the junction capacitance. Such a capacitance variation is associated with charge carrier redistribution in the near-surface region of the substrate when the trapped charge is embedded. This feature of the C–V characteristic can be used to detect a local charge embedded in the insulating layer of a field-effect transistor.

It has been shown experimentally that upon local bombardment of NaCl, KCl, and KBr crystals with 50-keV electrons, sodium and potassium nanoparticles with plasmon resonances in the visible spectral region are formed in these crystals. We have obtained optical-density spectra of crystals after the bombardment with electrons in various doses. The probability of location of nanoparticles in the solid or liquid phase, as well as interference effects emerging in the irradiated zone of crystals, have been studied using numerical simulation.

Polarization characteristics of the field of an on-Earth emitter located at the Kola Peninsula are experimentally measured at a distance that is no greater than the height of an effective ionospheric waveguide in the FENICS-2014 experiment. Variations in the field amplitude and orientation of the major axis of polarization ellipse are observed at lower frequencies upon significant changes of the K index of geomagnetic activity. Polarization characteristics of the horizontal component of magnetic field calculated with allowance for the ionosphere and two-layer Earth structure prove the observed sensitivity of the ultralow- and lower-frequency filed in the near-field zone to the state of ionosphere at lower conductivity of underlying medium. Theoretical results are compared with the experimental data. The results are important for deep sounding of the Earth and monitoring of ionosphere with the aid of controlled low-frequency ground sources.

On the basis of numerical simulation of heating of symmetric contacts with flowing current, conclusions were drawn about the accuracy of determining the temperature by the Holm–Kohlrausch method for various methods of cooling the contacts, including with intensive air and liquid cooling. The possibility to apply this method at pulse heating of the contacts has been considered. The dependence of accuracy of determination of the temperature of contact pads on the choice of points of measurement of the surface temperature and potential difference has been revealed.

We consider the concept of effective potential, that has been proposed recently based on analysis of stroboscopic sampling of coordinates and velocities of ions moving in an rf quadrupole field. Exact expressions have been obtained for the stroboscopic model of motion of ions, which are valid at any point of a stability zone. Analysis of these expressions has led to correction of some postulates of the initial effective potential concept of stroboscopic sampling, which was developed for the neighborhood of the stability zone peak.

Escape zone depths λ' for true-secondary electrons and photoelectrons from pure CdTe and CdTe with a Ba film of thickness θ ≤ 1 monolayer have been estimated for the first time. It is shown that upon a decrease of the work function of the surface by 2 eV, the value of λ' increases by 1.2–1.3 times.

A desktop NMR relaxometer was created, which allows determining spin–spin relaxation times of water protons in living tissues. Spin relaxation times of protons of water reflect changes in the mean number of paramagnetic centers, since the presence of these centers increases the magnetization recovery rate of water protons in living tissues tens of times. In particular, this method allowed observing age-related changes (sarcopenia) related to substitution of connective tissue for muscle fibers. Relaxometers of this type are comfortable to use and are promising devices for analysis and diagnostics of changes and disorders of metabolic processes.

At present, the development of magnetic levitation transportation is conducted based on electromagnetic and electrodynamic suspensions the technical and commercial implementation of which has been successfully demonstrated in Korea, China, Japan, and other countries. Sources of an electromagnetic field in suspensions can be normally conducting electromagnets, superconducting magnets and high-coercive permanent magnets. The progress made in the development of new magnetic materials (permanent magnets and high-temperature superconductors) opens up prospects for reducing the energy consumption of levitation transport systems. The authors proposed magnets of all three types, which together ensure the functioning of combined electromagnetic suspension, and created scale models of such magnets. The permanent levitation of suspension models with a load is provided. The correctness of technical solutions is confirmed, software created in the Russian Federation allows one to reliably-scale magnetic systems of suspensions. Thus, all the prerequisites have been completed for the next stage of creating full-scale prototypes of effective levitation systems, in particular, a 50-ton cargo platform.