The high-volage penonena in aluminum Molten chloride electrolytes

L. A. Kazieva, S. I. Suleymanov.

ABSTRACT

The electrical conductivity of the molten chloroaluminates NaAlCl4 and KAlCl4 increases with increasing of electrical field strength and reach the limiting values (the Wien effect) which surpass their usual low-voltage conductivity up to 200 and 700 percent respectively. These results have been obtained on the base of analysis of the microsecond high-voltage discharges in the melts (the Wien effect). After the high-voltage pulses discharges having been completed in the melts, their conductivity and electrolyze current have been found to rise up to 50% and their decomposition potentials has found to decrease more than 20% (the “memory effect”). The relaxation time of a non-equilibrium state reaches 5 minutes and more.
KEY WORDS

activation, melts, chloroaluminates, Wine effect, relaxation, structure, aluminum, conductivity.

Li2O solubility in LiCl-KCl melt

V. A. Kovrov, A. R. Mullabaev, V. Yu. Shishkin, Yu. P. Zaikov

ABSTRACT

Crystallization temperatures (liquidus and solidus) in the systems LiCl-Li2O and (LiCl-KCl)-Li2O with the KCl containing 10 and 20 mol.% were obtained with independent methods of thermal analysis of cooling curves, isothermal saturation, and differential scanning calorimetry. The linear sweep voltammetry was applied to control the time of the equilibrium establishment in the molten system after the Li2O addition, which depended on the composition of the base melt and the concentration of Li2O. The fragments of the binary LiCl-Li2O and quasi-binary [LiCl-KCl(10 mol.%)]-Li2O and [LiCl-KCl(20 mol.%)]-Li2O phase diagrams in the Li2O concentration range from 0 to 12 mol.% were obtained. The presence of KCl in the LiCl-KCl-Li2O molten mixture in the amount of 10 and 20 mol.% reduces the liquidus temperature by 30 and 80 degrees, respectively, but the region of the homogeneous molten state of the system is considerably narrowed, which complicates its practical application. The Li2O solubility in the molten LiCl, LiCl-KCl(10 mol.%) and LiCl-KCl(20 mol.%) decreases with increasing of KCl content and is equal to 11.5, 7.7 and 3.9 mol.% at 650 °C, respectively.

KEY WORDS

lithium chloride, potassium chloride, lithium oxide, liquidus, solidus, solubility, pyro-chemical reprocessing, spent nuclear fuel.

Physicochemical foundations for the synthesis of zinc oxide in molten chlorides

T. A. Rozdjalovskaja.

ABSTRACT

The results of the investigation of chloride ions oxidation during the oxygen bubbling through zinc and alkali metal (Na, K) chloride melts at 600 °C are presented. The amount of gaseous chlorine produced depends on the molar ratio of chlorides in the mixture. It is shown that the amount of released chlorine is directly proportional to the values of the effective polarizing force of the cations. The kinetic characteristics of chlorine formation were determined and calculated: the reaction order, reaction rate constants, and the activation energy values. Particle size, chemical composition, and surface area for some samples of ZnO were determined.

KEY WORDS

zinc and alkali metals chloride melts, zinc oxide production, molten chlorides oxidation.

LaCoO3-d as an Oxygen Electrode Material for the Molten Carbonate Fuel Cell. Part 2. Catalytic activity of LaCoO3-d for oxygen reduction in (Li0.62K0.38)2CO3 melt

S. I. Vecherskii, M. A. Konopelko, N. N. Batalov, M. A. Zvezdkin, I. V. Zvezdkina.

ABSTRACT

Kinetics of oxygen reduction on “in situ” lithiated LaCoO3-d electrode in (Li0.62K0.38)2CO3 melt has been studied. It has been shown that under the experimental conditions the main electroactive species are superoxide ions and molecular oxygen, which correlates with studies on a gold electrode. However, the observed mechanism of the electrode reaction differed from the mechanisms proposed for the gold electrode. A number of mechanisms accounting the peculiarities of the oxide electrode have been proposed. Exchange current densities were found to be independent on the oxygen partial pressure and varied in the range 220–290 mA/cm2, depending on the experimental conditions and the supposed mechanism.

KEY WORDS

molten carbonate, fuel cell, perovskite, lanthanum cobaltite, oxygen reduction, electrocatalytic activity.

LaCoO3-d as an Oxygen Electrode Material for the Molten Carbonate Fuel Cell. Part 1. Electrophysical Properties of lithiated LaCoO3-d.

S. I. Vecherskii, M. A. Konopelko, B. D. Antonov, N. N. Batalov, M. A. Zvezdkin, I. V. Zvezdkina.

ABSTRACT

Oxides LaCoO3-d + (z/2) Li2O (0 ≤ z ≤ 0.15) were synthesized and studied to elucidate variation of electrophysical properties of LaCoO3-d due to lithiation “in situ” in (Li0.62K0.38)2CO3 eutectic melt. It has been found that a perovskite-like solid solution (La1-хLix)(LiхСо1-х)O3-d, where х = z/(z + 2), forms as a result of doping by Li. The solid solution region does not exceed 2х = 0.072. At higher lithium content LiCoO2 appears along with the main perovskite-like phase. Single-phase samples exhibit a metallic type of conductivity and positive thermopower at the molten carbonate operating temperature 920 K. Electrical conductivity of Li-doped samples is 1.5 or less time smaller compared to LaCoO3-d, it varies in the range 3.2 × 104–3.8 × 104 S/m.

KEY WORDS

molten carbonate, fuel cell, perovskite, lanthanum cobaltite, electrical conductivity.

Extraction of scandium and zirconia from their oxides electrolysis of oxide fluoride melt

V. Suzdaltsev, A. A. Filatov, A. Yu. Nikolaev, A. A. Pankratov, N. G. Molchanova, Yu. P. Zaykov.

ABSTRACT. The main regularities of extraction of scandium and zirconium from their oxides into aluminum during aluminothermic and electrolytic preparation of Al-Sc and Al-Zr alloys and ligatures in KF-AlF3, NaF-AlF3 and KF-NaF-AlF3 oxide-fluoride melts with Sc2O3 additives and ZrO2. The effect of the melt composition and its temperature, the duration of synthesis, the content of Sc2O3 and ZrO2 oxides in melts, the mechanical mixing of aluminum and the cathode current density on the content of scandium and zirconium in aluminum, and their extraction from oxides are determined. It is shown that, depending on the synthesis parameters, the average values of extraction of scandium and zirconium are 20–75 and 40–100%, respectively. The electrolytic decomposition of oxides in melts KF-AlF3, NaF-AlF3 and KF-NaF-AlF3 leads to a significant increase in extraction of scandium and zirconium into aluminum. Based on the results of the research, the parameters for obtaining alloys and ligatures Al-Sc and Al-Zr with scandium content up to 10 and zirconium up to 15 wt.% in the electrolysis of oxide-fluoride melts.

KEY WORDS: scandium, zirconium, oxide-fluoride melt, aluminothermy, electrolysis, extraction.

Influence of the content of fluorine in alkaline on the indicators of aluminum electrolysers of the Kazakhstan electrolysis factory

Zh. Zh. Kamzin, V. A. Lebedev

ABSTRACT:

For two series of electrolysis, a regression analysis of the dependences of the average voltage, current yield, specific power consumption on the fluorine content in fluorinated alumina (CF), received for electrolysis, was performed. An increase in CF by 1% is accompanied by a slight increase in average voltage (5–10 mV), a significant (by 0.5–1.1%) reduction in current output and an increase (by 110–170 kW h/t) in the specific consumption of electricity. To improve the electrolysis, it is necessary to lower the fluorine content in fluorinated alumina.

KEY WORDS:

fluorinated alumina, fluorine content, average voltage, current efficiency, specific power consumption, regression analysis.

Selective dissolve of brass in the melted evetectic mixture of carbonates of lithium, sodium, potassium

E. V. Nikitina, N. A. Kazakovtseva, N. K. Tkachev,

E. A. Karfidov, M. A. Maikov, V. B. Malkov

ABSTRACT:

The possibility of dissolving brass of grade L63 in a melt of alkali metal carbonates at an operating temperature of 773 K in potentiostatic and galvanostatic regimes is shown. It was found that the pore size and quantity depend on the electrochemical parameters, on the applied potential or current density.

KEY WORDS:

brass, copper alloys, selective dissolution, dealloying, anodic polarization

Conductivity of melts in mixtures of gadolinium trichloride with sodium and potassium chlorides

K. I. Trifonov, I. F. Zabotin, S. F. Katyshev, A. F. Nikiforov

ABSTRACT:

The values of specific conductivity of melted mixtures of gadolinium trichloride with sodium and potassium chlorides have been determined. The values of molar conductivity for the examined salt mixtures have been calculated, and the isothermal projection of molar conductivity for the triple system GdCl3–NaCl–KCl is presented. Analysis of the results received makes it possible to offer a hypothesis on the nature of the components interaction.

KEY WORDS:

specific and molar conductivity, gadolinium chlorides, sodium and potassium, interaction of components.

Potential activity coefficient, dissolved in moltables of its halogenides

V. M. Ivenko, V. V. Chebykin, L. A. Tsiovkina

ABSTRACT:

The parameters of the equations for the activity coefficient of potassium dissolved in KF–KCl, KF–KBr, KF–KI and KCl–KI melts with molar ratio of salt components of 3 : 1, 1 : 1, 1 : 3, as well as in equimolar melts KCl–KBr and KBr–KI. The concentration of potassium in the melts varied, from about 1 to 10 mol %. A representation of the authors on the complex structure of solutions of an alkali metal in mixtures of its halides is given, which makes it possible to understand the dependence of the thermodynamic properties of potassium dissolved in them.

KEY WORDS:

solutions, melts, alkali metals, halides of alkali metals, activity, activity coefficient.