E. E. Shpil'rain

Activity of the Components of Binary Alloys of Alkali Metals: Na–K System

The activity coefficients of the components of the Na–K binary system are determined proceeding from the thermodynamic conditions of liquid–vapor equilibrium. The obtained data are in satisfactory agreement with the results of calculation of these activity coefficients by the pattern of the liquidus curve and using integral heats of mixtures of sodium–potassium alloys, as well as with the experimental data obtained by the emf method and by the effusion method.

New Data on the Solubility of Inert Gases in Liquid Alkali Metals at High Temperature

The solubility of helium, neon, argon, krypton, and xenon in molten lithium, sodium, potassium, rubidium, and cesium is calculated in the ranges of temperature from 600 to 1500 K and pressure from 0.1 to 10 MPa. The calculated data are compared, in comparable ranges of the parameters of state, with the results of the experimental investigations available in the literature of the solubility of inert gases in liquid alkali metals.

The Pressure of Saturated Vapors of Liquid Alloys of Alkali Metals at High Temperatures: Na–Rb System

The pressure of saturated vapors of a molten Na–Rb system is calculated from the experimental data on the activity coefficients of the components of this system at temperatures of 773 and 1073 K in a wide range of its compositions available in the literature [1, 2]. The calculated values of the saturation pressure of liquid sodium–rubidium alloys are compared with the results of an experimental investigation of the ps–Ts dependence for a Na–Rb alloy containing 60.78 at. % Rb [3].

Investigation of Pyrolysis of Methane under Conditions of Filtering through a Heated Porous Medium

An unsteady-state one-dimensional mathematical model is used to perform a theoretical analysis of the process of thermal decomposition of methane under conditions of filtering through a heated porous medium formed by granules of commercial-grade carbon. A scheme of the process kinetics is developed. The effect of the basic characteristics of commercial-grade carbon and of the operating conditions on the efficiency of the process is treated. Laboratory experiments are performed in support of the commercial-scale technology of production of granular pyrocarbon. A comparison of the calculation results with experimental data demonstrates their good agreement.

Concentration correlation function in liquid alkali-metal mutual solutions up to 1200K

Abstract The dependencies of concentration correlation function Scc(0) = f(xi) have been plotted on the isotherms of 400, 800, 1200K on the basis of the obtained experimental data within the temperature range from the liquidus line to 1300K. The efficiency of the use of this function has been discussed as an instrument for estimation of the magnitude of the concentration fluctuations and stability of the solution as a single-phase homogeneous system, reliability of the experimental data on Gibbs energy of formation for solution ΔG and methods of their approximation as well as reliability of the theoretical models which reproduce the behaviour of ΔG, internal consistency of the data when the self-contained thermodynamic description of mutual liquid metal solutions is building.

Experimental Investigation of the Activity of Sodium in a Liquid Sodium–Potassium Alloy in a Wide Temperature Range

The EMF method is applied to investigate the activity of sodium in a molten sodium–potassium alloy containing 87.2 wt. % of potassium. The measurements are performed in two different experimental setups. One of them uses glass containing sodium ions as electrolyte, and the other one uses beta-ceramics. Therefore, the limiting experimental temperature in the first case does not exceed 550 K, while in the second case, it is about 750 K. The maximal relative error of the experimental data on the activity of sodium in a liquid Na–K alloy is approximately 3%. The discrepancy between the measurement results and the experimental and theoretical data available in the literature is within this error.

Activity of the Components of Binary Alloys of Alkali Metals: K–Cs System

The experimental data on the pressure of saturated vapors of a molten potassium–cesium system are used to determine the activity of its components at high temperatures. The obtained results are compared with the values of activity of potassium and cesium in liquid K–Cs alloys, which are calculated using their heats of mixture.

Internally consistent thermodynamic description of three-component liquid-metal systems at high temperatures in the entire region of concentration triangle

A method is suggested for the investigation of the thermodynamic properties of ternary liquid-metal alloys at high temperatures in the entire region of concentration triangle. The method is demonstrated for a Na–K–Cs ternary system. Data are obtained for the enthalpy and Gibbs energy of formation of alloy in the temperature range of 200 ≤ T≤ 1200 K and concentration range of 0 ≤ xi (  j , k)≤ 1. The results reveal a very fine effect associated with the temperature rise, namely, the inversion of excess partial Gibbs energy ΔG¯i*= RT ln γi(γiis the activity coefficient of the liquid component) and the change of sign of deviation of partial pressure, as well as of total pressure, from the respective values in accordance with Raoults law. The obtained results may be used to interpret the available literature data on independent measurements of the saturation pressure.

Analysis of the Singular Features and Internal Consistency of the Thermodynamic Properties of Binary Alkali-Metal Coolants, Based on the Correlation Function of Concentration Fluctuations

The stability of a binary liquid-metal alloy as a homogeneous single-phase system is analyzed; a criterion is validated for the estimation of the internal consistency of the thermodynamic and structural properties, as well as of the reliability of the experimental data on the Gibbs energy of solution formation ΔG and of the methods for approximating these data, and of the theoretical models reproducing the ΔG behavior in systems of alkali metals. The analysis is based on the construction of the correlation function of concentration fluctuations Scc(0) = f(T, xi) using the experimental data obtained in the range of temperatures 400 ≤ T ≤ 1200 K and concentrations 0 ≤ xi ≤ 1 for Cs–Na, K–Na, and Cs–K systems.

The Activity of the Components of a Na–K–Cs System at High Temperatures

The activity coefficients of the components of a Na–K–Cs ternary system in a temperature range of 773–1200 K are determined using the previously calculated thermodynamic properties, in particular, the activity of the components of binary alloys of alkali metals such as Na–K, Na-Cs, and K–Cs, at high temperatures [1–3]. The sides of the triangle of the phase diagram of this system are constituted by the binary Na–K, Na–Cs, and K–Cs binary alloys. The results obtained are used to calculate the saturated vapor pressure of the sodium–potassium-cesium eutectic (22.1 wt % K and 73.8 wt % Cs [4, 5]) in the same temperature range. The calculated data are in good agreement with the recommended reference data [6].