Cd1-xZnxTe crystals are necessary for the production of ionizing radiation detectors widely used in science, technology, medicine and other fields. Internal stresses during crystallization lead to generation of dislocations and low-angle boundaries. Typical problem of melt crystal growth of Cd-Zn-Te compounds are tellurium inclusions, which deteriorate detector performance. Microgravity conditions provide unique opportunities for growing high-quality crystals due to the absence of convection, more equilibrium conditions of melt mixing, and a decrease in internal stresses. Since the properties of such crystals strongly depend on the production conditions, seeds and a feed ingot with specified compositions and structure are required. Ampoules with two compositions of materials have been prepared for the space experiment. Crystals of different compositions Cd0.96Zn0.04Te and Cd0.9Zn0.1Te were produced for two charges. They consist of an oriented seed, solvent, and feeding ingot, which are single-phased, single crystalline, have certain crystallographic orientation, meet demands for growth of Cd–Zn–Te crystals in microgravity. Ampoules containing these materials were sent to International Space Station for crystal growth on equipment already assembled at “Nauka” station.

An impact mill has been developed to produce powders from shavings of refractory metals using the impact grinding method for reuse in electrometallurgy in devices with screw feed, for example, in 3D printers. The proposed device provides high uniformity of grinding with a minimum content of dust fraction and impurity content at low technical and economic costs. The result is achieved using a Laval nozzle, which operates in the supersonic jet formation mode. In the area of the first Mach disk, there are rod fenders arranged in a cascade, and the impact plate is located in the turbulence zone and is equipped with winglets with holes for separating crushed metal.

Large-size Cd0.9Zn0.1Te crystals were grown using high-pressure vertical zone melting. It has been found that Te inclusions ranging 70-150 mu m with density 3.5 & sdot;102 cm- 2 are formed during crystal growth under conditions specified in this work. Optical spectra display the transmission of the CZT crystals in near- and medium infrared range, which is close to theoretical value and does not degrade despite presence of Te inclusions. Based on the obtained data on sizes and distribution of the inclusions, diffusion coefficient of tellurium in CZT was estimated for Te particles entrapped by growing interface. The calculated value (1.22-3.2)& sdot;10- 8 cm2/s most probably indicates vacancy mechanism of diffusion. Density of in-grown dislocations revealed by chemical etching is 4 & sdot;104 cm- 2. Branched 3D dendrites are found in CZT crystals.

Wereport the preparation of bulk ingots of a spin-polarized Ti2MnAl zero-gap semiconductor (Heusler alloy). Ti2MnAl was prepared from elemental titanium, manganese, and aluminum by levitation melting via high-frequency induction heating in an argon atmosphere and by electric-arc skull melting in a helium atmosphere. The melt solidification mechanism and kinetics have been studied in detail.

Экспериментально установлено, что эмиссионные свойства источников на основе углеродных нанотрубок деградируют после 20 часов выдержки в жидком гелии и улучшаются после двухчасовой выдержки в атмосфере водорода при давлении 100 атм и температуре 300 °С.

The multilevel nature and plasticity of memristor structures based on bismuth selenide microcrystals (of the "flake" type), which are controlled by the rewriting voltages Vset/Vreset are investigated. It was shown by numerical simulation that the switching is caused by the barrier properties of the defective layer, consisting of two sublayers having different thicknesses, as well as different electrical and thermal conductivities, overheating phenomena have been also taken into account. The change in the device resistance both at ON-OFF and at OFF-ON transitions begins at approximately the same absolute value of the threshold electric field of the order of 10(5) V/cm. Modulation of the barrier formed at the interface between a metal and a strongly doped semiconductor is the most likely model for resistive switching in bismuth selenide-based structures. (C) 2020 Elsevier Ltd. All rights reserved.

A study is performed of different conditions of the synthesis and growth of perfect crystals of the family of Mott insulators for creating memristors (new-generation memory elements). The ceramic synthesis of GaNb4Se8 compound is used in combination with the thermolysis of niobium selenides under nonequilibrium conditions, allowing a material with a high level of chemical uniformity to be created.

The protection of DC power circuits against short circuits in the load is considered and a possibility of preventing emergencies is demonstrated during operation of pulse power supplies feeding the AC electric arc, which is a complex load for output stages of an inverter. The proposed scheme was implemented and tested in an arc power supply for the development of 3D-printing technology using local segregation electric arc melting.

We experimentally investigate charge transport through the interface between a gold electrode and a black phosphorus single crystal. The experimental dI/dV(V) curves are characterized by well developed zero-bias conductance peak and two strongly different branches. We find that two branches of asymmetric dI/dV(V) curves correspond to different band gap limits, which is consistent with the theoretically predicted band gap reconstruction at the surface of black phosphorus under electric field. This conclusion is confirmed by experimental comparison with the symmetric curves for narrow-gap (WTe2) and wide-gap (GaSe) metal-semiconductor structures. In addition, we demonstrate p-type dopants redistribution at high bias voltages of different sign, which opens a way to use the interface structures with black phosphorus in resistive memory applications.

Исследовался механизм, возможность и условия применения эффекта бистабильных резистивных переключений в структурах на основе халькогенидов в устройствах памяти и мемристорах как альтернативных функциональных материалов по сравнению с оксидами, традиционно разрабатываемых сегодня. The report highlights the mechanism, possibility and conditions of applying the effect of bistable resistive switching in structures based on the connection of metal selenides in memory devices and memristors as alternative functional materials in comparison with the oxides traditionally developed today.

We present the results of experimental studies of the effect of hydrogen absorption on the emission properties of a charge source based on carbon nanotubes. It is determined that the emission properties of the source improve considerably after exposure in hydrogen atmosphere at pressure of 100 atm and temperature of 300°С for 2 hours: at voltage of 300 V the current of negative charges increases by 104 times.

We experimentally compare two types of interface structures with magnetic and non-magnetic Weyl semimetals. They are the junctions between a gold normal layer and magnetic Weyl semimetal Ti$_2$MnAl, and a ferromagnetic nickel layer and non-magnetic Weyl semimetal WTe$_2$, respectively. Due to the ferromagnetic side of the junction, we investigate spin-polarized transport through the Weyl semimetal surface. For both structures, we demonstrate similar current-voltage characteristics, with hysteresis at low currents and sharp peaks in differential resistance at high ones. Despite this behavior resembles the known current-induced magnetization dynamics in ferromagnetic structures, evolution of the resistance peaks with magnetic field is unusual. We connect the observed effects with current-induced spin dynamics in Weyl topological surface states.

Transitions in the resistive switching of diode heterostructures based on bismuth selenide, in which bipolar resistive switching is implemented, are investigated. It is found that the time of transitions from one metastable state to another has a fast component on the order of microseconds and a slow component (a shuttle tail). Results are described using the model of a critical electric field, and the parameters of the investigated structures are calculated numerically.

— The original equipment has been developed and the feasibility has been shown of manufacturing shaped products from refractory metals by 3D printing using a high-pressure electric arc in a protective gas atmosphere. The proposed technique is performed using layer-by-layer metal deposition using local electric arc skull melting. In experiments aimed at manufacturing molybdenum crucibles, it has been shown that the speed of 3D printing is higher by 2–3 orders of magnitude than the speed of printing by selective laser sintering.

contact with the ampoule walls and absence of plastic deformation of the crystal under its own weight. For improvement of the fullerite C60 crystal growth technology before the scheduled space experiments on the ISS the growing of the high purity grade fullerite C60 crystals with the sufficiently high structural perfection were carried out on the Earth from the C60 vapor in sealed quartz ampoules (pre-evacuated to the pressure of 10−3 Pa) at temperatures in the evaporation zone ranging from 560 – 610 ◦C with a temperature gradient between the evaporation and deposition zones of 3 – 10 K/cm within 72 h. The grown single crystals had a size of ∼ 5× 5× 5 mm and habitus corresponding to the fcc lattice. IR spectroscopy shows the high purity fullerite C60.

In this paper, we developed a production method for items based on mesh silicon carbide that are suitable for cleaning aggressive fluids, melts, and gases from foreign inclusions at high operating temperatures. The resulting products can also be used for filtering fuel mixtures.