Vol 52, No 3 (2016)

The paper considers the possibility to expand the number of materials used for electrospark alloying. Ceramic nanostructured TiB₂–TiC–Al₂O₃–ZrO₂-based materials produced by means of SHS extrusion are used as electrodes. The regularities of the alloyed layer formation with electrospark alloying (ESA) are studied. Three different modes of anode erosion and cathode gain are observed for single pulse energies ranging from 0.05 to 2.5 J. The microstructure of the coatings is studied. It is shown that, in the case of ESA by ceramic SHS electrodes, nanosized crystallites are formed. The microhardness of the alloyed layer is 1250 HV. The tribological tests of the protective coatings demonstrate a high wear resistance (10^–5 mm³/N/m) and low friction coefficient (0.2).

The paper deals with an investigation of mechanical properties and deformation features of polycrystalline copper and single-crystal LiF under dynamic nano/microindentation. It is shown that the values of hardness and Young’s modulus depend on the magnitude of the applied load (P_max): when the load is increased, H and E decrease. General regularities of the indenter penetration process in a wide range of loads are revealed: the appearance of a “pop-in” effect at the initial stage of the loading process, the formation of more pop-in steps with the growth in load, and the formation of pileups around the indentations. Such a nature of deformation is the result of sequential activation of different dislocation mechanisms with indenter deepening. Along with a great similarity in the specificity of deformation, some differences are noted at the unloading stage. The results serve to compare the mechanical properties of Cu and LiF individual components with similar parameters of the “coating/substrate” composite systems (CS Cu/LiF) produced on their basis.

A procedure for calculation of basic parameters of the baroelectric treatment of an Al–Al₃Ti–Ti multilayer package in the synthesis of the Ti–Al₃Ti monolithic metal–intermetallide laminate from a set of Al–Ti foils is proposed. Loading conditions at which the treatment time substantially decreases in comparison with hot isostatic compaction are shown.

The article is devoted to the results of research on the influence of electrodischarge cavitation and of the electromagnetic field of a discharge current on the physicochemical properties of water. The aim of the research is the development of basics of the tactics for increasing the water absorption intensity by a solid mass of organic fibers during their treatment. Part I deals with the initial properties of the electrodischarge working medium and main methodical points of investigation.

This study deals with the energy efficient and enviromentally safe methods of electronic treatment of water-containing foodstuffs in order to extend their shelf life without changing their initial nutrition and biological properties. It is shown that high-voltage electric pulse treatment of fluid foodstuffs, instead of thermal pasteurization and sterilization, is less power consuming in both the processing time and the temperature of heating the medium. It is found that the following requirements must be satisfied to reach the total inactivation of microorganisms in the treated fluid medium: temperature of heating the medium in the discharge chamber must be higher than the critical one in the range of ~70°C; the high electric field intensity between the electrodes must not cause a breakdown of the medium; the pulse amplitude should be maximal; the pulse front should be minimal (up to 20 ns); and the pulse duration has to be optimally long (no less than 100 ns). It is ascertained that the high-voltage pulse treatment with these parameters leads to the improvement of the properties of the treated beverages, the acquisition of new curative properties, and the extension of their shelf life.

A hydrothermal technique for the express synthesis of a composite based on carbon nanotubes (CNTs) and manganese dioxide by means of the direct reduction of potassium permanganate from an aqueous isopropanol solution is proposed in this work. The synthesis conditions (time, temperature, ratios between reagents) are optimized; the primary and secondary processes taking place in the system are considered in detail. The synthesized CNT/MnO₂ composite is studied with the help of a wide range of physicochemical and electrochemical methods to assess the possibility of its use as a positively charged electrode of an asymmetric supercapacitor (SC). The assembled SC cell based on this composite and an activated carbon (AC) electrode has fairly high power typical of conventional electric double-layer capacitors (0.82 kW/kg) with a twofold increase in the energy density (12.14 W h/kg).