Spin-Thermoelectric Effects in a Quantum Dot Hybrid System With Magnetic Insulator

We investigate spin thermoelectric properties of a hybrid system consisting of a single-level quantum dot attached to magnetic insulator and metal electrodes. Magnetic insulator is assumed to be of ferromagnetic type and is a source of magnons, whereas metallic lead is reservoir of electrons. The temperature gradient set between the magnetic insulator and metallic electrodes induces the spin current flowing through the system. The generated spin current of magnonic (electric) type is converted to electric (magnonic) spin current by means of quantum dot. Expanding spin and heat currents flowing through the system, up to linear order, we introduce basic spin thermoelectric coefficients including spin conductance, spin Seebeck and spin Peltier coefficients and heat conductance. We analyse the spin thermoelectric properties of the system in two cases: in the large ondot Coulomb repulsion limit and when these interactions are finite.

Disposal of copper electrofining solutions

The paper presents studies of the processing of spent copper electrolyte from the processing of non-ferrous metal scrap at a copper smelter in Kazakhstan. For the processing of the spent electrolyte, a stage-by-stage neutralization was carried out using zinc sublimates and potash. As a result of the first stage of neutralization with zinc sublimations to pH 4.7, a precipitate with a content of PbO 44.69 %; PO2 16.36 % was obtained. After processing the sediment with an alkaline solution, carbonization and melting at a temperature of 900 oC, metallic lead and tin-containing slag with a content of SnO2 of 16.36 % were obtained. As a result of the second stage of neutralization with potash to pH 7.1, a precipitate was obtained-with a CuO content of 76.45 %. After the third stage of neutralization with potash to pH 9.5, a precipitate with a content of NiO 27.63 % and ZnO 55.75 % was obtained. After treatment of the precipitate with a solution containing 100 g / dm3 KOH, a zinc-containing solution with a ZnO content of 225.0 g/dm3 and a precipitate were obtained, after calcination of which nickel oxide with a NiO content of 89.14 % was obtained.

Electrochemical Production of Bismuth in the KCl–PbCl2 Melt

An anode dissolution of binary metallic lead–bismuth alloys with different concentrations of components has been studied in the KCl–PbCl2 molten eutectic. The dissolution of lead is found to be a basic process for the alloys of Pb–Bi (59.3–40.7), Pb–Bi (32.5–67.5), Pb–Bi (7.0–93.0) compositions in the whole interval of studied anode current densities. A limiting diffusion current of lead dissolution was observed at 2 A/cm2 and 0.1 A/cm2 for the alloys of Pb–Bi (5.0–95.0) and Pb–Bi (3.0–97.0) compositions, respectively. The dissolution of bismuth takes place at the anode current densities exceeding the mentioned values. The number of electrons participating in the electrode reactions is detected for each mechanism. Based on the theoretical analysis, the experimental electrolysis of bismuth was performed in the laboratory-scale electrolytic cell with a porous ceramic diaphragm. The final product contained pure bismuth with a lead concentration of 3.5 wt.%.

Investigation of quantum transport and local density of states in a graphene strip connected to a square lattice

We theoretically express quantum transport at Dirac points via graphene quantum billiard as a non-magnetic material to connect metallic leads. Our results indicate that the quantum billiard of graphene is similar to a resonant tunnelling device. The centerpiece size and the Fermi energy of the graphene quantum billiard play an important role in the resonant tunnelling. In graphene, change of carrier density can affect plasmon polaritons. At the Dirac point, the conductivity of graphene depends on the geometry, so that the conduction of the evanescent modes is close to the theoretical value of 4e2/πh (where Planck's constant and the electron charge are denoted by h and e, respectively.). This transport property can be used to justify chaotic quantum systems and ballistic transistors. Our theoretical results demonstrate that the local density of state of the graphene sheet for EL = ER = 0 is larger than EL = ER = t (where EL (ER) is onsite energy of the left (right) metallic lead) unlike the current obtained from the calculations.

Lead extraction as metallic phase from waste lead oxide-containing glass by redox reaction in hydrothermal treatment

A new low-energy and eco-friendly method for extracting lead from waste PbO-containing funnel glass is required. Conventional methods use either energy intensive smelting reduction at temperatures higher than 1273 K or involve phase separation of the glass, requiring an acid treatment to extract elemental Pb partitioned in one of the decomposed phases as Pb2+ ion. In this study, the mechanism of a unique phenomenon is investigated, involving spontaneous precipitation of metallic lead when PbO-containing glass is subjected to a hydrothermal water environment in a stainless-steel container. The roles of the hydrothermal environment and container materials on the metallic lead precipitation were investigated. The synthesized PbO-containing glass was placed in a container made of stainless steel or pure iron and set in a sealed autoclave with water, which was held at 613 K to provide the hydrothermal conditions. As a result, metallic lead droplets precipitated either on the surface of the glass or the container, whereas an iron oxide (Fe3O4) phase was detected on the surface of the container. Conversely, no metallic lead was observed when the glass and stainless-steel container were heated in dry air. The above results indicate that a hydrothermal environment is necessary for metallic lead precipitation because subcritical water or steam leaches Pb2+ from the glass. In addition, a redox reaction was suggested between the Pb2+ ions transported to the surface of the container and metallic iron in the container to explain metallic lead droplets precipitation.

Spectacular Enhancement of the Thermal and Photochemical Stability of MAPbI3 Perovskite Films Using Functionalized Tetraazaadamantane as a Molecular Modifier

Perovskite solar cells represent a highly promising third-generation photovoltaic technology. However, their practical implementation is hindered by low device operational stability, mostly related to facile degradation of the absorber materials under exposure to light and elevated temperatures. Improving the intrinsic stability of complex lead halides is a big scientific challenge, which might be addressed using various “molecular modifiers”. These modifiers are usually represented by some additives undergoing strong interactions with the perovskite absorber material, resulting in enhanced solar cell efficiency and/or operational stability. Herein, we present a derivative of 1,4,6,10-tetraazaadamantane, NAdCl, as a promising molecular modifier for lead halide perovskites. NAdCl spectacularly improved both the thermal and photochemical stability of methylammonium lead iodide (MAPbI3) films and, most importantly, prevented the formation of metallic lead Pb0 as a photolysis product. NAdCl improves the electronic quality of perovskite films by healing the traps for charge carriers. Furthermore, it strongly interacts with the perovskite framework and most likely stabilizes undercoordinated Pb2+ ions, which are responsible for Pb0 formation under light exposure. The obtained results feature 1,4,6,10-tetraazaadamantane derivatives as highly promising molecular modifiers that might help to improve the operational lifetime of perovskite solar cells and facilitate the practical implementation of this photovoltaic technology.