Standard rate constants of charge transfer for the redox couple Ti(IV)/Ti(III) in chloride-fluoride melts with the different cationic composition

The influence of the second coordination sphere of titanium complexes on the charge transfer kinetics of the Ti (IV)/Ti (III) redox couple in melts of alkali metal halides was studied by cyclic voltammetry method. Diffusion coefficients in the CsC-CsF (10 wt. %) melt were calculated. The standard rate constants of charge transfer have been determined by the Nicholson method. The activation energies of the charge transfer process in (NaCl- KCl)equimol-NaF (10 wt. %) — K2TiF6, KCl-KF (10 wt. %) — K2TiF6 and CsCl-CsF (10 wt. %) — K2TiF6 melts were calculated.

Microstructural Master Alloys Features of Aluminum–Erbium System

Aluminum master alloys with rare earth metals are widely studied by many scientists around the world, but research on the production of Al-Er master alloys is still limited. The purpose of this work is to study the microstructure parameters of aluminum-erbium master alloys obtained by metallothermic reduction of salt mixtures containing erbium oxide or fluoride. The structural features were investigated by optical and scanning electron microscopy, and the dependence of the microhardness of the eutectic and solid solution fields of obtained master alloys on the content of erbium in the master alloy was determined. Studies have shown that master alloys obtained by metallothermic reduction of erbium compounds from chloride–fluoride melts are characterized by a uniform distribution of Al3Er intermetallic compounds in the volume of double eutectic [(Al) + Al3Er] and have a strong grain refinement effect. The analysis of the microstructure showed that the structure of the master alloys varies depending on the content of erbium. When the content of erbium in the master alloy is up to 6 wt.%, the eutectic structure is preserved. When the content of erbium in the master alloy is 8 wt.% or more, the structure becomes a solid solution with individual inclusions of various shapes and intermetallic compounds.

Comparative analysis of modern methods of production of Al – Zr ligatures

A brief overview of modern industrial and experimental methods for the synthesis of aluminozirconium ligatures is performed. The basic regularities of the proceeding processes, and also properties of the obtained ligatures are considered, technical and economic indicators and prospects of development of the considered technologies are estimated. The comparative estimation of key parameters of the most promising technologies for industrial application is carried out, the influence of temperature, a mode of synthesis and a kind of initial raw materials on profitability of the process is estimated. Aluminothermic and electrolytic methods of ligature synthesis are considered in more detail, the views of other authors on the kinetics of ongoing processes are taken into account, and an overview of the influence of electrolyte composition and electrolysis mode on the structure and properties of produced alloys is presented. It has been shown that, depending on the method, in a wide temperature range (80 – 1000 oC), Al – Zr master alloy with a zirconium content up to 57 wt.% can be obtained. However, all existing methods for the production of Al – Zr master alloys have significant drawbacks, which lead to the relatively high cost of the master alloys, the presence of hazard waste and low production efficiency. It is concluded that along with the current methods of direct fusion of metals and aluminothermic synthesis, it is promising to obtain ligatures by electrolysis of oxide-fluoride melts KF – NaF – AlF3 using zirconium oxide as the main metalcontaining raw material. The results of experimental testing of a new method for obtaining Al – Zr master alloys via electrolysis of oxide-fluoride melts are presented. It has been established that the developed technology makes it possible to maximize the extraction of zirconium from the oxide, to continuously obtain master alloys with a high zirconium content, excluding the accumulation of unclaimed waste. The study was performed with the financial support of the Russian Foundation for Basic Research within the research project No. 19-33-90144.

FLUORITE INLAID BY BASNÄSITE FROM SYENITES OF THE VELYKOVYSKA MASSIF (UKRAINIAN SHIELD) AS EVIDENCE OF THE EXISTENCE OF A CARBONATE-FLUORIDE MELT

A millimeter-sized fluorite crystal found in leucocratic syenite of the Velykovyska massif on the Ukrainian Shield became the object of study. This is a crystal of irregular shape with smoothed corners, broken by a system of contraction cracks inlaid with basnäsite-(Ce). The latter is characterized by a REE content of 57± 5 wt. %, CaO - of 3.3 ± 0.25 wt. % and Ce2O3 : La2O3 : Nd2O3 ratio of 6 : 4 : 1. A detailed study using microprobe JXA-733 and an electron microscope JSM-6700F, equipped with EDS JED-2300, showed the presence of other mineral phases in the inlays. The middle of the cracks is filled with ferrous aluminosilicate without REE. On the opposite side, a siderite rim was found around the basnäsite and single crystals of calcite were found nearby in the fluorite. Fluorite inlaid with basnäsite is considered as a product of crystallization of the carbonate-fluoride melt drop that separated from silicate melt due to their immiscibility. Subsequent stratification of the melt inside the drop led to formation of fluorite rimmed by carbonates of REE and Fe and displaced to the cracks of Fe-aluminosilicate. Crystallization of the separated carbonate-fluoride melt took place in an isolated volume without any exchange of components with the surrounding Na-K-feldspar. Fluorite, as well as carbonates and mica are less common in the Velykovyska massif than other similar syenite massifs on the Ukrainian Shield. It is assumed that this is caused by the high temperature of the syenite melt, which contributed to evaporation of volatile components (F2, CO2, H2O), and by processes of liquation. The immiscibility between salt and silicate melts contributed to formation of drops of carbonate-fluoride melt and their movement to the apical parts of the massif and outside. The discovery of inlaid fluorite increases the prospects of the Velykovyska massif for the detection of REE ore occurrences in syenites and surrounding rocks. In addition, the finding confirms the existence of carbonate-fluoride melts in nature. These melts are paternal for fluorite-carbonate veins with REE mineralization.