O. V. Samoilova

Thermodynamic analysis of the Cu-Si-Ni-O system

The liquidus surface of the Cu2O-SiO2-NiO ternary phase diagram is constructed. It is shown that the peritectic reactions occur in the ternary diagram; due to them, a the existence region of nickel olivine Ni2SiO4 with oxide melt manifests itself. A solubility surface of components in the metal of the Cu-Si-Ni-O system for a temperature of 1200°C is constructed.

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.

Constructing Isotherms of Oxygen Solubility in the Liquid Metal of the Cu-Na-K-O System

The thermodynamic modeling of phase equilibria in the liquid metal of the Cu–Na–O, Cu–K–O and Cu–Na–K–O systems in the temperature range of 1100–1300 °С was done. The calculations were performed using the methodology of constructing a surface of component solubility in the metal melt, which does not only allow us to calculate the isotherms of oxygen solubility in the molten metal, but also to link the changes in the composition of such molten metal with quality changes in the composition of the interaction products. The isotherms of the oxygen solubility in the liquid metal of the Cu–Na–O, Cu–K–O and Cu–Na–K–O systems were constructed.

Thermodynamic Assessment of the Na-Cu and Na-K Binary Systems

The Na–Cu and Na–K systems present a big interest for the study due to the use of liquid sodium and melt of sodium and potassium in the nuclear industry as a coolant in nuclear reactors. In the present work, thermodynamic modeling of phase equilibria in the Na–Cu and Na–K systems is carried out, based on the available published experimental data. This modeling was done using the “FactSage” software package (version 7.0). The set of Redlich–Kister equation parameters was obtained, that allows to describe the dependence of Gibbs energy from composition and temperature for solutions that can be formed in the studied systems. Phase diagrams (T–x diagrams) of the investigated systems were calculated.

Thermodynamic Simulation of the Phase Diagram of the Cu2O–Na2O–K2O System

Thermodynamic simulation of phase equilibria is carried out, allowing us to calculate the liquidus lines for the phase diagrams of the Cu2O–Na2O, Cu2O–K2O, and K2O–Na2O oxide binary systems, and also the liquidus surface of the Cu2O–Na2O–K2O ternary system. In the course of the work, the values of the model parameters used to calculate the activity of the oxide melts of the investigated systems are determined. The values of the activity of copper oxide and sodium oxide in the Cu2O–Na2O system for a temperature of 1250°C are calculated. The activity data are characterized by negative deviations from Raoult’s law. During the simulation, the enthalpy and entropy of the formation of a KNaO compound from the liquid components are estimated. According to the calculations, the liquidus surface of the phase diagram of the Cu2O–Na2O–K2O ternary system has two points of invariant equilibria.

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.

Phase Equilibria in Liquid Metal of the Cu–Al–Cr–O System

A thermodynamic analysis of phase equilibria in the Cu–Al–Cr–O system is carried out. Thermodynamic modeling of the liquidus surface of the Cu2O–Al2O3–Cr2O3 oxide phase diagram is performed. To describe activities of an oxide melt, the approximation of the theory of subregular ionic solutions, the energy parameters of which were determined during modeling, is used. Melting characteristics of the CuCrO2 compound are also evaluated in the course of the calculation. Coordinates of invariant equilibria points implemented in the Cu2O–Al2O3–Cr2O3 ternary oxide system are established by the results of the calculation. Thermodynamic modeling of interaction processes in the Cu–Al–Cr–O system in occurrence conditions of a copper-based metal melt is also performed. The temperature dependence of the equilibrium constant of the reaction that characterizes the formation of the CuCrO2 solid compound from components of the metal melt of the Cu–Al–Cr–O system is determined. The temperature dependence for the first-order interaction parameter (by Wagner) of chromium and oxygen dissolved in liquid copper is found. The results of thermodynamic modeling for the Cu–Al–Cr–O system are presented in the form of the solubility surface of components in metal, which makes it possible to attribute the quantitative variations in the metal melt concentration with qualitative variations in the composition of forming interaction products. It is determined by the results of modeling that particles of the |Al2O3, Cr2O3|sol.sln solid solution are formed at valuable aluminum and chromium concentrations in the copper melt of the Cu–Al–Cr–O system as the main interaction product. The results of the investigation can be interesting for improving the technology process of smelting of chromium bronzes.