In this article  we have  analyzed radioactive isotope applications in the technology of autonomous power  supplies and the materials used in radioisotope thermoelectric generators (RTGs), justified  the  advantage of manufacturing betavoltaic generators, compared them with other electric power sources and considered the mechanism of β−decay and positioned it among other types of nuclear transformations. We have  also  drawn  up the  basic radiation safety requirements to the  materials used for the  hull and  the  converter, analyzed some earlier  designs of radioisotope betavoltaic sources and set up a list of isotopes suitable as energy sources in betavoltaic generators. Furthermore, we have  analyzed methods of obtaining radioactive materials which exhibit β−decay, their  basic properties and  abundance in nature. In conclusion, the  choice of nickel−63 isotope has  been selected as preferable for betavoltaic generators due to the optimum combination of half−life, average particle energy and radiation intensity.

The regularities of impurity distribution between the distillate and the still as well as the spatial  distribution of impurities  along  the distillate length have been studied. We conclude that some impurities such as s−metals, Zn, Ni, V and rare metals distribute uniformly along the distillate length (20 cm). Contrarily, Se tends to concentrate in the distant (from the still) region  of distillate with more  than one order  of magnitude higher concentration compared to the nearest region.

In this work, mathematical modeling was used to optimize the geometry of the composite mold for developing the technology of equal−channel angular pressing with three channels for thermoelectric materials. To obtain the maximum degree of deformation in this work, we used a three−channel scheme. Taking into consideration the material characteristics (low resistance to tensile  stresses), we proposed a tapering profile (along  the length)  of the third channel. To analyze the  plastic  flow in the  proposed scheme of equal−channel angular pressing with three channels, we performed mathematical modeling of plastic flow, stress and deformation rates along the rod, deformation homogeneity along the cross−section and absence of stagnant zones in the extruder. The methodical approach is based on the combined use  of the elastic and plastic  solid state approximations according to the fundamentals of the elasticity and plasticity theory. Critical points are identified having the maximum stored energy accumulation without discontinuity of the material. Calculation of the flow velocity in planes perpendicular and  parallel  to the  deformation axis showed a slight difference in the flow rate of the material  for the section plane parallel to the deformation axis. This produces a bend with a large  curvature radius  but  does not  cause cracking of the  material. Calculation of deformations along  the  flow axis allowed  us to detect deformation inhomogeneity. This resulted in the  appearance of small  tensile stresses in the longitudinal  section of the third channel. We show that the plastic  deformation inhomogeneity revealed by modeling can be eliminated by using an equipment design with a greater output channel length. Mathematical modeling shows the suitability of the suggested unconventional design of equal−channel angular pressing equipment for bismuth chalcogenide base solid solutions.

Studies of ionic conductivity  and structures in which it can be achieved are of great importance for the development of modern batteries. The use of new materials will allow avoiding such typical disadvantages of batteries as short service life, low capacity and leaks. In this article we present the results of our study of the ionic conductivity in boron  carbon nanolayers. We have simulated three types  of boron carbon nanolayers containing different amounts of boron. The studies have been carried out using the MNDO method within the framework of the  molecular cluster model  and  the  DFT method with the  B3LYP functional  and the 6−31G basis. To study the ion conduction process we have simulated vacancy formation for each type of the nanolayers and studied the energy and electronic characteristics of these processes. We show that 25 % boron substitution is the most energetically favorable for vacancy formation. We have  also  simulated vacancy migration  and  determined the  thermal conductivity  as  a function  of temperature.

The features and  regularities of self−assembly and  self− organization processes in the diffusion−limited conditions (method of drops) of aqueous (deionized water) colloidal solutions of multi−walled carbon nanotubes with aerosil under the influence of constant electric fields with a value varying of direct  current voltage  from 15 to 25 V have been studied. During droplet evaporation in an electric field, the processes of hierarchical structuring have been studied and the formation of linear piecewise with the sizes of 40—120 nm, fractal structures 25—45 nm and  diffusion structures 250 nm from MWCNT — COOH + aerosil  + H₂O_DI  have  been observed. These structures have  been analyzed by methods of confocal microscopy, X−ray powder diffraction, Raman scattering, atomic force microscopy, FT−IR spectroscopy and scanning electron microscopy. The size of micro− and nanostructures in hyperbolic dependence of d = 1/U in the  approximation d → 2R, and their growth rate  increases as U² have been observed. Intensive ultrasonic dispersion proves to produce a centrally−axial arrangement located SWCNT after ultrasonic dispersing of functionalized MWCNT — COOH + aerosil  + H₂O_DI colloidal solution, as confirmed by excitation of Raman lines in the low−wavelength region, the so−called breathing mode, resulting in the existence of mixed types sp²−hybridization with π− and σ−carbon bonds, as well as metallic and semiconducting conductivity, which indicates great practical importance of this structuring for the development of nanoelectronics.

This work deals with structural transformations in the near− surface layers of silicon after  ion beam synthesis of zinc−containing nanoparticles. Phase formation after  Zn ⁺ ion implantation and  two−stage O⁺ and Zn⁺ ion implantation followed by thermal annealing in a dry oxygen atmosphere was studied. To avoid amorphization, we heated the substrate to 350 °C during the implantation. After implantation, we annealed the samples for 1 h in a dry oxygen  atmosphere at 800  °C. The structure of the surface silicon layers was examined by X−ray diffraction and transmission electron microscopy. We show that a disturbed near  surface layer with a large  concentration of radiation induced defects appears as  a result  of 50 keV Zn⁺ ion implantation. In the  as−implanted specimens, metallic  Zn nanoparticles about 25 nm in size formed at a depth of 40 nm inside  the damaged silicon layer. Subsequent annealing at 800 °C in a dry oxygenatmosphere produced structural changes in the defect layer, formed Zn₂SiO₄ nanoparticles at a depth of 25 nm with an average size of 3 nm and oxidized the existing Zn particles to form the Zn₂SiO₄  phase. The oxidation  of the metallic  Zn nanoparticles starts from the surface of the particles and leads to the formation of particles with a “core−shell” structure. Analysis of the phase composition of the silicon layer after O⁺ and  Zn⁺ ion two−stage implantation showed that Zn and  Zn₂SiO₄ particles formed in the  as−implanted state. Subsequent annealing at 800 °C in a dry oxygen  atmosphere increases the particle  size but does not change the phase composition of the near surface layer. ZnO nanoparticles were  not observed under the  experimental ion beam synthesis conditions..

This paper reviews the literature concerning the specifics of creating Ohmic contacts to AlGaAs/GaAs heterostructures with a 2D electron gas with high electron mobility. The process of annealing the  contacts based of the  Ni/Au/Ge  system is considered, and  the recommended parameters of the  metalization layers are  borrowed from the  literature. This process allows reproducible fabrication of Ohmic contacts with a low electrical resistance to temperatures below 4K. Several mechanisms are  analyzed which could  result  in the experimentally observed dependence of the contact parameters on crystallographic orientation. A method of contact fabrication with Au/ Ge/Pd metallization is described for which the contact is formed by mutual  diffusion and  interaction of the metals and  the semiconductor in the  solid phase at temperatures below  200  °C. This provides for high composition homogeneity of the contacts, a smooth metal / semiconductor boundary and can reduce the effect  of orientation on the electric characteristics of the contact.

The family of bismuth ferroelectrics with a layered structure have for more than half a century caused great interest of researchers from theoretical and practical viewpoints. Theoretical interest is due to the specific structure of the compounds with high-temperature blurred ferroelectric transition, while practical one stems from the possibility of obtaining multifunctional materials. This work deals with the crystallochemical analysis of the least−studied species of the family, i.e., the simplest compositions of the “Bi₂O₃ − second oxide” type and complex precipitation structures, i.e., compounds with the so−called mixed−layered lattice structure.We suggest crystallochemical formulae to describe the compositions of the abovementioned structure types. We expect these formulae to provide for a more focused synthesis of new compounds of the family.