G. G. Mikhailov

Sorption properties of silicate materials based on Ca2SiO4

Sorption studies showed that a silicate material formed in the course of metallurgical slag reprocessing, containing dicalcium silicate as the major component, exhibits high affinity (logKd [ml g−1] > 4) for U(VI), Pu(IV), REE(III), and Th(IV) cations and for simple anions and appreciable affinity (logKd [ml g−1] > 2) for Cs(I) and Sr(II) cations in their sorption from river water. The sorbent can be of practical interest for separation, preconcentration, neutralization, and recovery of harmful chemical elements and radioactive substances from aqueous solutions, followed by their cementation (solidification) and safe disposal.

Thermodynamic description of the interaction processes in the Cu–Ce–O system in the temperature range 1100–1300°C

A thermodynamic simulation and an experimental study of the interaction between cerium and oxygen in liquid copper have been performed. The thermodynamic analysis of the interaction processes in the Cu–Ce–O system is carried out using the technique of constructing the surface of solubility of components in a metal in the temperature range 1100–1300°C. As a result of simulation, data on changes in the Gibbs energy ΔGT° and the equilibrium constants of formation of cerium oxides Ce2O3 and CeO2 from the components of a copper-based metallic melt are obtained. The first-order interaction parameters (according to Wagner) of cerium and oxygen dissolved in liquid copper, namely, eCeCe, eOCe, and eCeO, are evaluated. Experimental studies of the Cu–Ce–O system have been performed. The morphological features, the size, and the composition of nonmetallic inclusions formed as a result of interaction in the Cu–Ce–O system are studied using scanning electron microscopy and electron-probe microanalysis.

Thermodynamic simulation and an experimental study of the possibility of synthesizing hardened Cu–Zr–O alloys

The conditions of formation of hardened Cu–Zr–O alloys are determined theoretically and experimentally. Thermodynamic analysis of the possibility of formation of zirconium oxide in a liquid metal is performed by constructing the surface of component solubility in a metal melt. Disperse zirconium oxide inclusions in samples are detected by scanning electron microscopy and electron-probe microanalysis. The hardness and the electrical conductivity of experimental samples are measured in the as-cast state and after cold deformation. Hardness HV 133 is reached in cold-deformed samples containing 0.05 wt % Zr without heat treatment. The results obtained can be used to create a process for the formation of bulk composite materials based on copper and copper alloys.

Thermodynamic Modelling of Rare-Earth Elements - Oxygen Interaction

Fusibility curves of FeO–La2O3–Al2O3, FeO–Ce2O3–Al2O3, La2O3– Ce2O3–Al2O3 oxide systems are created based on the literature data and modern thermodynamic theories of oxide and metal melts. Admitting the oxide systems conjugation with the area of metal melts existence, we define oxide phases, which can maintain the equilibrium with metal melts of Fe–Ce–Al–O, Fe–La–Ce–Al–O systems. The surfaces of component solubility are created for above mentioned metal melts. For Fe–Ce–Al–O system it is established that the following phases can be at equilibrium with metal: Al2O3, Сe2O3, FeO∙Al2O3, Сe2O3∙11Al2O3, Сe2O3∙Al2O3, and the oxide melt (FeO, Al2O3, Сe2O3, СeO2). For Fe–La–Ce–Al–O system the following oxide phases can be at equilibrium with the liquid metal: La2O3, Al2O3, Сe2O3, La2O3∙Al2O3, Сe2O3∙11Al2O3, Сe2O3∙Al2O3, and the oxide melt (FeO, La2O3, Al2O3, Сe2O3, СeO2). Diagrams of active components consumption, which are used to establish the possibility of chosen equilibrium, are created for iron deoxidation with cerium and aluminium as well as with Ce and La at fixed Al content (0.01 wt. %).

Thermodynamic modeling of the reaction of lanthanum with components of iron-based melts

Thermodynamic analysis of binary and ternary oxide systems containing the oxide La2O3 permits the formulation of a database of energy parameters in the theory of subregular solutions for oxide melts adjacent to the region of existence of metallic melts in the phase diagram of the system. The temperature dependence of the equilibrium constants for the heterogeneous reduction of steel is established. The solubility surfaces of components in oxygen-bearing steel are plotted for the Fe–Al–La–O–C, Fe–Ca–La–O–C, Fe–Mg–La–O–C, Fe–Si–La–O–C, and Fe–Cr–La–O–C systems. Diagrams are plotted for the complex reduction of steel by alloys and mixtures containing active and alloying elements: Ca, Mg, Si, Al, Cr, and La. Analysis is undertaken for thoroughly reduced and sulfur-free steel. With the usual reduction system, in which rare-earth metals are added to the steel after the introduction of calcium, silicon, and aluminum, the inclusions that form—consisting of a conglomerate of calcium and magnesium aluminates—provide the substrate for the deposition of small fractions, actively interact with the liquid component of the inclusions, and dissolve in the liquid component. Therefore, La2O3 is not present as an independent phase in the metallic inclusions.

Thermodynamics of steel modification by barium and cesium alloys

On the basis of experimental, production, and literature data, appropriate parameters for the theory of subregular ionic solutions are determined. Solubility surfaces for the components are plotted, for low-alloy and carbon steel and also for multicomponent alloys.

Distribution of dopant metals between PbTiO3 crystals and PbO-B2O3 flux

Single crystals of lead titanate PbTiO3 doped with silicon, calcium, chromium, manganese, cobalt, nickel, copper, zinc, and cadmium were grown. The compositions and crystallographic parameters of the crystals were studied. The lowest distribution coefficients of dopants between PbTiO3 crystals and flux were observed with Mn+2 and Co+2 and the highest, with Ca+2. Doping with niobium leads to the formation of solid solutions with the pyrochlore structure A2B2O7 and even higher distribution coefficient. A correlation was found between dopant concentrations and crystal cell parameters.

Reduction of iron oxides in a humid atmosphere

103 The reduction of metal oxides by gaseous and solid agents is fundamental to metallurgical technologies. In view of its importance, the existing theoretical and applied research must be periodically reviewed and sometimes corrected. Thermodynamic analysis of the reduction of iron oxides in binary gases H2–H2O and CO–CO2 permits very precise determination of the parameters of equi librium states for individual reduction reactions [1]. However, practically all reduction processes involve complex gas mixtures [2] and multicomponent con densed phases. In that case, thermodynamic analysis is complicated by the dozens of reactions that occur. The parameters of such equilibria are listed in huge tables, while the literature lacks relevant graphs, although three dimensional diagrams and their iso thermal cross sections would often be useful. In the present work, we propose a systematic approach to the physicochemical interpretation of the equilibrium parameters for iron ore reduction in a humid atmosphere, for the systems

Thermodynamic Analysis of Copper Melt Deoxidation with Lanthanum

Using rare earth metals as deoxidizers is an efficient way of getting highly deoxidized copper melt required for certain bronzes production. Thermodynamic modeling of phase equilibria in the Cu–La–O system in the temperature range of 1100–1300 °С was performed to assess a possible depth of copper melt deoxidation with lanthanum, and also to determine the resulting oxide phases. During the experimental part of the work, Cu–La–O system metal samples were melted and then studied with the JEOL JSM 6460-LV scanning electron microscope equipped with the energy-dispersive spectrometer providing electron microprobe analysis to specify formed nonmetallic inclusion type.

Thermodynamic Modeling of Phase Equilibrium in Fe-Y-Cr-C-O Liquid Metal System

The thermodynamic characteristics of processes in the liquid metal system Fe–Y–Cr–C–O are considered as applied to low-carbon and low-alloy metal. The critical parameters for the state diagram of the oxide system Y2O3–Cr2O3 were established based on the values quoted in literature. The temperature dependence of the melting reaction constant Y2O3·Cr2O3 was determined. The coordinates of eutectic transformation points for the system Y2O3–Cr2O3 were calculated. In accordance with subregular solution theory, the energetic parameters which are necessary to calculate the activities Cr2O3 and Y2O3 of oxide melts in the system Y2O3–Cr2O3 were determined. The energetic parameters of subregular solution theories for the oxide system FeO–Cr2O3–Y2O3 were determined based on the values for the binary systems FeO–Y2O3, FeO–Cr2O3 and Y2O3–Cr2O3. The view of this diagram, as coupled with the existence domain of liquid metal within the framework of the quaternary system Fe–Y–Cr–O–С, suggests that low-carbon chromic liquid metal when injected with yttrium can form the following non-metallic inclusions: |Cr2O3|, |Y2O3|, |FeO·Cr2O3|, |Y2O3·Cr2O3| or oxide melt (FeO, Y2O3, Cr2O3). Oxide melt may contain up to 2 % of divalent chrome (Cr2+). The equilibrium constants for the main reactions of steel deoxidation with the formation of liquid, solid and gas products of chemical reactions were also established. The activity of components dissolved in metal was calculated using interaction parameters. The set of derived expressions for the activity of components and the dependences of equilibrium constants of chemical reactions and phase transformations allowed us to diagram the surface of component solubility in liquid metal (SCSM). SCSM diagrams show the compositions of liquid metal and indicate oxide phases which are in equilibrium with liquid metal.