Vol 2018, No 2 (2018)

The results of studying the formation of short- and intermediate orders in amorphous alloys and a long-range order in nanocrystalline alloys in quenching of metallic melts show that the structures of metal atom groups in both states consist of both icosahedral and helicoidal packings, which coherently combine crystalline and noncrystalline coordinations due to fractional symmetry.

The effect of the chromium concentration on the magnetic properties of Fe–Cr precursors for hard-magnetic Fe–Cr–Co materials is studied. Nitrogen used as a sintering atmosphere and a long annealing time enhance are found to increase the coercive force H_c of the materials. The phase formation in Fe–30% Cr alloys is traced during heat treatment in nitrogen and argon atmosphere using thermal analysis.

The electrode capacitance is determined as a function of potential by measuring the capacitance and the impedance of a rhenium electrode in NaCl, KCl, and CsCl melts at various temperatures and ac signal frequencies, and the impedance parameters are calculated. The capacitance curve is shown to have two minima in these systems and an additional third minimum in sodium and potassium chlorides. This third minimum disappears when temperature increases. The potential of the cathode minimum of capacitance measured at an ac signal frequency of about 10³ Hz coincides with the corresponding minimum of the capacitance of the double electrical layer. The potentials of the central and anode minima of capacitance measured at a frequency of about 1 Hz coincide with the potentials of the minima of adsorption capacitance.

The main features of scandium and zirconium extraction from their oxides to aluminum during the aluminothermic and electrolytic preparation of Al–Sc and Al–Zr alloys and master alloys in the KF–AlF₃, NaF–AlF₃, and KF–NaF–AlF₃ oxide–fluoride melts with Sc₂O₃ and ZrO₂ additives are studied. The influence of the melt composition and temperature, the synthesis time, the contents of oxides Sc₂O₃ and ZrO₂ in the melts, the mechanical stirring of aluminum, and the cathodic current density on the contents of scandium and zirconium in aluminum and on their extraction from the oxides is determined. The average values of scandium and zirconium extraction are 20–75 and 40–100%, respectively, depending on the synthesis parameters. The electrolytic decomposition of the oxides in the KF–AlF₃, NaF–AlF₃, and KF–NaF–AlF₃ melts results in the enhancement of scandium and zirconium extraction to aluminum. The parameters of the preparation of Al–Sc and Al–Zr alloys and master alloys with the scandium content to 10 wt % and zirconium content to 15 wt % during the electrolysis of oxide–fluoride melts are chosen as a result of the results obtained.

Oxides LaCoO_{3 – δ} + (z/2) Li₂O (0 ≤ z ≤ 0.15) are synthesized to determine the boundaries of changing the electrophysical properties of LaCoO_{3 – δ} due to its in situ lithiation in the (Li_0.62K_0.38)₂CO₃ eutectic melt. A perovskite-like solid solution (La_{1 – x}Li_x)(Li_xCo_{1 – x})O_{3 – δ}, where x = z/(z + 2), is found to form as a result of Li doping. The region of existence of the solution does not exceed 2x = 0.072. At a higher concentration of Li, LiCoO₂ forms along with the perovskite-like phase. At the operating temperature of the carbonate fuel cell (T = 920 K), the single-phase samples have metallic conduction and positive thermopower. The electrical conductivity of the Li-doped samples decreases as compared to that of LaCoO_{3 – δ} by no more than 1.5 times and varies from 3.2 × 10⁴ to 3.8 × 10⁴ S/m.

The oxidation of chloride ions in molten mixtures of zinc chloride and alkali metals (Na, K) is studied during oxygen bubbling at a temperature of 600°C. The dependence of the quantity of formed chlorine on the molar ratio of the chlorides in a mixture is found. The quantity of formed chlorine is shown to be directly proportional to the effective polarizing power of a cation. The following kinetic characteristics of the oxidation of chloride ions with respect to chlorine are calculated: the order of reaction, the reaction rate constants, and the apparent activation energy. Zn oxide is extracted and the dispersity, the chemical composition, and the specific surface area of some samples are determined.

The no-current diffusion saturation method is used to study the possibility to synthesize a powder Co₂Er intermetallic compound in the molten eutectic mixture of lithium and potassium chlorides at a fixed temperature of 850 K. Based on the results obtained, the conditions of synthesizing the powder Co₂Er intermetallic compound of a given composition are determined. The range of metallic-phase component blending ratios for a reaction mixture is determined; within this range, the powder compound free from impurity intermetallic compounds and unreacted base metal (powder cobalt) can be synthesized. The reliability of the results obtained is confirmed by X-ray fluorescent and X-ray diffraction analyses using an EDX-720 energy dispersive X-ray fluorescent spectrometer and an XRD-700S diffractometer, respectively.

The conductivities of the disperse system α-Al₂O₃–molten carbonate chloride mixture Li₂CO₃–Na₂CO₃–K₂CO₃–NaCl are dtermined in the temperature range 455–550°C. As follows from Raman spectroscopy data, α-Al₂O₃ does not interact chemically with the carbonate–chloride melt in this temperature range. The force and energy characteristics of the CO₃^2- anion in the systems are revealed.

Classical molecular dynamics simulation is used to calculate the self-diffusion coefficients of the ions that make up reciprocal molten LiF–RbBr and LiF–CsBr mixtures at a temperature of 1420 K over the entire concentration range. The microscopic motion of the fluoride ion is shown to change qualitatively as a function of the nature of the cation forming the nearest environment. For example, the nearest environment of the fluoride ion in a reciprocal LiF–RbBr mixture at a low rubidium bromide concentration favors an increase in its self-diffusion coefficient despite the fact that the system density increases in this case.

The discharge characteristics of a thermally activated battery element with cathode materials based on CrCl₃–MoO₃ mixtures are studied. The composition and the morphology of the products of reduction of the cathode materials are determined. A mechanism is proposed for their reduction to metallic chromium and molybdenum through an intermediate stage of formation of the melts of the complex Li₃CrCl₆ compound and lithium molybdates with lithium chloride.

Impedance spectroscopy is used to study the electrical conductivities of the borosilicate and aluminophosphate glasses containing analogs of the high-level fuel-processing waste of VVER-440. The electrical conductivities of the aluminophosphate and borosilicate glasses are found to be mainly determined by the sodium oxide concentration and to change significantly with temperature. An empirical equation is obtained to describe the electrical conductivity of the borosilicate glasses as a function of the sodium oxide concentration and temperature. The influence of the analogs of the HLW components on the electrical conductivities of the melts in the concentration range under study is insignificant.

Page 625, left column, line1, should read: “coolants in nuclear reactors” instead of “heat-carrying agents in nuclear rectors.”

Symbol “α_p” should read instead of “α_m”.