Fabrication of rare-earth metals by metallothermic reduction: Thermodynamic modeling and practical realization

At the present time, rare-earth elements in metallurgy are used in the form of mischmetal – a rare-earth elements natural mixture (with atomic numbers from 57 to 71). It contains about 50 wt. % of cerium. The remaining elements are mainly lanthanum and niobium. The specific composition is determined by the ore deposit. Inconstant composition of the modifier containing rare-earth metals (REM) can significantly reduce its efficiency. Experimentally, for every branded steels composition the ratio of various REMs can’t be selected because of the high costs of obtaining technically pure rare-earth metals. The task of determining the each rare earth element optimum concentrations and complex ligature composition can be solved by thermodynamic modeling. In the framework of thermodynamic modeling, the interaction between magnesium, aluminum and lanthanum with oxygen in liquid iron is presented. And the thermodynamic model of steel deoxidation by these active metals composition is considered. On the basis of available literature data on the phase diagrams of the systems MgO – Al2O3 , MgO – La2O3 and La2O3 – Al2O3 , the coordinates of the invariant equilibria points in the system MgO – La2O3 – Al2O3 were determined. The phase diagram of the system MgO – La2O3 – Al2O3 was constructed. It made possible to establish all phase equilibria realized in the process of deoxidation of steel with magnesium, lanthanum and aluminum and to describe these phase equilibria by chemical reactions equations. The activity of the components in liquid oxide melts was determined using the theory of subregular ionic solutions, which takes into account the dependence of the coordination number of cations on the composition of the oxide melt. The activity of components in metal melts conjugated with oxide systems were determined by Wagner’s theory using the parameters of the first order interaction. Equilibrium constants values for the steel deoxidation reactions are installed indirectly by thermodynamic calculations. On the basis of the obtained data the components solubility surface in the metal melts of Fe – Mg – Al – La – O system was constructed, which allowed to determine the liquid metal composition regions associated with the corresponding oxide phase.

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The industrial preparation of the rare earth metals by metallothermic reduction

JOM ◽

10.1007/bf03378760 ◽

1968 ◽

Vol 20 (11) ◽

pp. 41-45 ◽

Cited By ~ 1

Author(s):

John L. Moriarty

Keyword(s):

Rare Earth ◽

Rare Earth Metals ◽

Metallothermic Reduction ◽

Industrial Preparation ◽

The Rare Earth

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Thermodynamic Studies and Optimization of the Method for Obtaining Neodymium Fluoride for the Production of Magnetic Sensors’ Sensitive Elements

Sensors ◽

10.3390/s21248361 ◽

2021 ◽

Vol 21 (24) ◽

pp. 8361

Author(s):

Andrei N. Kropachev ◽

Sergey V. Podrezov ◽

Alexander V. Aleksakhin ◽

Andrey A. Gudilin ◽

Olga A. Kondratyeva ◽

...

Keyword(s):

Rare Earth ◽

Chemical Transformation ◽

Rare Earth Metals ◽

Magnetic Sensors ◽

High Tech ◽

Metallothermic Reduction ◽

Elemental Fluorine ◽

Sensor Material ◽

Advantages And Disadvantages ◽

Master Alloys

Rare earth metals (REM) with magnetic properties find application in the recently developed high-tech industries. Sensor magnetic systems based on neodymium are increasingly in demand in modern engineering and geological surveys due to their favorable combination of properties of magnetic materials based on rare earth metals. One of the problems is to obtain high-quality materials for the production of such magnetic sensors. It should be noted that the high activity of REM does not allow obtaining master alloys and REM-based alloys from metallic materials; it is advisable to use halide compounds. This work discusses a method for producing neodymium fluoride from its oxide. REM fluorides can be obtained by fluorinating the oxides of these metals. Various fluorine-containing compounds or elemental fluorine are usually used as fluorinating reagents, which have their own advantages and disadvantages. The thermodynamic and technological analysis of neodymium fluoride production processes has shown the most acceptable fluorinating agent is ammonium hydrofluoride, which was used in this work. In order to increase the productivity and degree of chemical transformation, it was proposed to perform heating stepwise; i.e., at the initial stage, heat at a speed of 3 degrees per minute, after which the heating speed was reduced to 2 degrees per minute, and finally the speed was reduced to 1 degree per minute. Due to proposed heating mode, the same productivity and yield of chemical transformation were achieved, with an increased efficiency up to 30%, which can significantly reduce the cost of production. The obtained product is used in the production of neodymium-based alloys by metallothermic reduction of a mixture of fluorides. The sensor material obtained in this way is characterized by a low (less than 0.05%) oxygen content.

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