Specifics of percolation behavior in the polyether–carbon nanotube systems doped with LiClO<Subscript>4</Subscript>

The electrical properties of the polyether/carbon nanotube (CNT) systems doped with LiClO₄ inorganic salt are studied via impedance spectroscopy. The percolation thresholds are evaluated in the context of the standard percolation theory for the nanofilled systems based on polyethylene glycol and polypropylene glycol, being 0.45 and 0.5%, respectively. Two percolation thresholds are observed for the polyether–CNT–LiClO₄ systems. A modified percolation model with consideration of two percolation transitions is proposed.     

High-temperature luminescence in an n-GaSb/n-InGaAsSb/p-AlGaAsSb light-emitting heterostructure with a high potential barrier

The electroluminescent properties of an n-GaSb/n-InGaAsSb/p-AlGaAsSb heterostructure with a high potential barrier in the conduction band (large conduction-band offset) at the n-GaSb/n-InGaAsSb type-II heterointerface (ΔE _c = 0.79 eV) are studied. Two bands with peaks at 0.28 and 0.64 eV at 300 K, associated with radiative recombination in n-InGaAsSb and n-GaSb, respectively, are observed in the electroluminescence (EL) spectrum. In the entire temperature range under study, T = 290–480 K, additional electron-hole pairs are formed in the n-InGaAsSb active region by impact ionization with hot electrons heated as a result of the conduction-band offset. These pairs contribute to radiative recombination, which leads to a nonlinear increase in the EL intensity and output optical power with increasing pump current. A superlinear increase in the emission power of the long-wavelength band is observed upon heating in the temperature range T = 290–345 K, and a linear increase is observed at T > 345 K. This work for the first time reports an increase in the emission power of a light-emitting diode structure with increasing temperature. It is shown that this rise is caused by a decrease in the threshold energy of the impact ionization due to narrowing of the band gap of the active region.     

Influence of the annealing temperature on the phase composition of Al-0.55 wt % Zr cast alloy

The influence of temperature on the phase composition of a cast aluminum alloy which contains 0.55% Zr, 0.23% Fe, and 0.06% Si is investigated in order to substantiate the optimal annealing modes using the Thermo-Calc program. The phase composition is determined and the equilibrium compositions of the aluminum solid solution in the Al-0.55% Zr-0.23% Fe-0.06% Si at t = 200–650°C is calculated. It is shown that, when using multistage annealing, the maximal hardness and conductivity are attained at t = 400–450°C.     

Improving fatigue strength by producing residual stresses on surface of parts of gas-turbine engines using processing treatments

The paper deals with a comparison of results of measuring residual stresses and with the study of their effect on the fatigue strength of parts of gas-turbine engines after finish treatments by grinding, polishing, and surface plastic deformation.     

Self-oscillation of an elastic polyurethane coating in polishing

The self-oscillation of an elastic polyurethane coating in polishing is considered. Recommendations for enhancing surface quality are presented.     

Linear Homogenization in the Analysis of Cellular Structures Produced by Additive Technology

Russian Engineering Research - Linear homogenization is applied to cellular structures produced by selective laser melting (SLM). Samples of different materials with cells of different...     

Catalytically active composite materials with porous aluminum oxide matrix modified by γ-MnO<Subscript>2</Subscript> nanoparticles

Manganese dioxide has been deposited on the surface of an aluminum foil anodized in 3% solution of oxalic acid using the methods of thermal decomposition of manganese nitrate and potassium permanganate, as well as chemical synthesis, in the same solutions with intermediate drying and subsequent annealing. It has been demonstrated that the method of thermal decomposition of potassium permanganate is the most suitable for producing thermally stable “ultradispersed γ-MnO₂/nanostructured Al₂O₃/Al” composites. The produced composites are active in the reaction of oxidation of CO into CO₂ at temperatures above 180°C. Studies by means of the methods of scanning electron and atomic force microscopies have shown that the concentration and surface distribution of γ-MnO₂ particles depend on the morphological structure of aluminum oxide that is determined by conditions of the metal surface pretreatment and application of the pore broadening operation.     

Laws of spreading and operational evaluation procedure for induced seismicity in mines and in mining areas

The scope of the article encompasses features of natural and induced seismicity and the change in frequency plots when natural seismicity turns into natural-and-induced seismicity in mining areas and when induced seismicity becomes natural-and-induced seismicity in mines. It is shown how induced seismicity is connected with the subsidence of overlying strata in mines—seismic process propagates together with the subsidence but seismic activity lowers in the time of maximum subsidence and intensifies when subsidence ceases or decelerates. The authors lay emphasis on estimates of seismic activity in mines and give details of an integrated index F procedure tested in mines and adjusted within the 10 year-long period of application.     

New lead-acid battery for submersible vehicles

In this paper a new design of a container is detailed for sealed lead-acid battery operating overboard of a submersible vehicle in conditions of increased ambient pressure. Such a container is both a battery jar and a pressure compensator. It has been shown that a mandatory requirement for such container use is an application of a gelled-electrolyte. Authors have offered a two-stage technology of filling of accumulators without using vacuum pumping.