Synthesis of aluminium-erbium master alloys from chloride-fluoride melts

Ya. I. Kosov, V. Yu. Bazhin.

ABSTRACT:

Aluminum-erbium master alloy is destined to improve the physical and mechanical properties of aluminum alloys. Current energy intensive foreign technologies and absence of domestic technologies of preparation of Al-Er master alloy make it important to create a technology of the aluminothermic reduction of erbium compounds from chloride-fluoride melts. A thermodynamic analysis of the aluminothermic reduction of various erbium compounds has been carried out. Erbium fluoride was chosen as the preferred starting material, taking into account the physicochemical properties of the erbium compounds. The aluminothermic reduction of erbium fluoride in the salt mixture with sodium fluoride and potassium chloride, taking into account the formation of the intermetallic compound Al3Er, has a high thermodynamic probability. The thermodynamic values of the erbium complex compound have been determined by an indirect method, because of limited information. The аluminum-еrbium master alloys has been synthesized via aluminothermic reduction method in the ErF3-NaF-KCl melts with different ratio ErF3 /NaF and content of KCl in the temperature range 750–900 °C. The result of the investigation of microstructure and phase composition of the synthesized master alloys has been given. The investigation of phase composition of the flux used to synthesize the Al-Er master alloy has been carry out

KEY WORDS: master alloy, aluminum-erbium, aluminothermic reduction, flux, thermodynamic, microstructure, intermetallic compound, Al3Er.

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.

Solubility of silver in K–KCl melt, having a two-phase region

V. M. Ivenko, V. Yu. Shishkin

ABSTRACT:

The solubility of silver in a K–KCl melt at a temperature of 775°C and a change in the potassium content in the melt from 0 to 100 mol %, which has a stratification region at this temperature, is investigated. It is shown that the solubility of silver increases linearly with an increase in the concentration of alkali metal, and in molten potassium it is 4.1 mol % Ag.

KEY WORDS:

melts, solutions, silver, potassium, potassium chloride

Capacitance and impedance of rhenium in molten alkali chlorides

Ye. V. Kirillova

ABSTRACT:

Capacitance–potential dependences for rhenium electrode in molten NaCl, KCl, CsCl were obtained at various temperatures and ac frequencies. Impedance parameters were calculated. It was shown that the capacitance curves in these systems are generally parabolic with two minima, whereas three minima were found in sodium and potassium chlorides at relatively low temperatures. Cathodic potential of minimum capacitance measured within ac range 103 Hz coincides with the corresponding minimum of double layer capacitance obtained by impedance fitting. Medium and anodic potentials of minimum capacitance measured within ac range 1 Hz coincide with the two minima of adsorption capacitance.

KEY WORDS:

rhenium, molten alkali chlorides, capacitance, impedance, potential of minimum capacitance, adsorption