Thermodynamics of Melts Based on the Processing Technology of the Richest Rare Metal Ores of Tomtor Deposit
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MOPHYSICAL PROPERTIES OF MATERIALS
Thermodynamics of Melts Based on the Processing Technology of the Richest Rare Metal Ores of Tomtor Deposit L. M. Delitsyna, * and V. M. Batenina, ** a
Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia *e-mail: [email protected] **e-mail: [email protected] Received March 3, 2020; revised March 16, 2020; accepted March 30, 2020
Abstract—The causes of the decomposition of a complex, multicomponent, phosphate-silicate melt containing oxides of rare-earth elements (TR2O3) and heavy metals (Nb, Ta, Zr) into two equilibrial condensed melts with contrasting component distributions are determined. Each of the melts represents a new type of artificial raw material for the production of rare earth and heavy metals. The implementation of this process enables the industrial use of the richest Tomtor deposit of rare-metal ores, the processing of which is practically impossible with the currently mastered methods. DOI: 10.1134/S0018151X20040021
INTRODUCTION The liquidation1 model is widely used in the study of the processes of ore formations that occur during the differentiation of magmatic melts [1]. The phenomenon of melt segregation into simple, two-component MeO–SiO2 systems was recorded by I.V. Greig in the 1920s. It was experimentally shown that the MeO–SiO2 systems are characterized by wide areas of melt segregation at a temperature of 1693°C. Moreover, the very act of phase decomposition into two liquid phases proceeds at a very high speed. Attempts to explain the mechanism of the phase-segregation decay of melts from the standpoint of their structure, which began as early as 1940–1950s with the publication of the works of W. Warren and A. Pincus, E. Levin and S. Blok, V. Weil, F. Glasser, I. Warshau, and R. Roy, etc., were summarized in [2–4]. The tendency of the glass former and modifier to form cationoxygen coordination polyhedra was considered to be the main cause of melt segregation. With similarity in shape and size, immiscibility does not occur. If there is no such similarity, then, depending on the relative bonding strength of the competing cations, either immiscibility occurs or the melt becomes unstable and the liquidus line acquires an S-shape. In this case, a metastable segregation forms below the liquidus line in tempered glasses, but this is a completely different task related to the glassy state, in which all processes proceed at a high matrix viscosity, and the sizes of the coexisting phases are of the order of micrometers. 1 Liquidation
is separation of a homogeneous melt into immiscible liquids of different composition.
It was later shown in [2] that the electrostatic force interaction between melt ions, which results in the affinity of two different cations to organize independent oxygen polyhedra around themselves, should be considered the primary cause of the melt immiscibility. Phase separation requires, first, a certain degree of cation–oxygen interaction strength and, second, structural incompatibility of the resulting o
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