S. N. Skovorod'ko

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].

The Density of Liquid Sodium–Potassium Eutectic

The experimental investigations of the density of molten sodium–potassium alloys of eutectic composition, described in the literature, are briefly reviewed. This review is used to estimate the confidence error of the measurement results. The least squares method is used to simultaneously process the entire body of the experimental data on the density of the liquid Na–K eutectic. An approximating equation is derived for the temperature range from the melting point of the sodium–potassium eutectic to 1300 K. The mean-square error of the calculated values of the density of Na–K eutectic melt in the given temperature range is determined.

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.

Experimental Investigation of the Pressure of Saturated Vapors of Liquid Alloys of Alkali Metals at High Temperatures: Na–Cs System

The saturated vapor pressure of liquid potassium–cesium alloys of five compositions (15.0, 30.0, 50.0, 65.0, and 85.0 at. % Cs) is measured by the U-tube manometer method in the temperature range from 760 to 1289 K. The alloys are prepared by the weighing method at a fairly high purity of starting potassium and cesium (>99.99 wt % for each of the alkali metals). The confidential error of the experimental results is in the range from 1.0 to 1.5%. The approximating equations for the saturated vapor pressure of the investigated K–Cs alloys are derived from the statistical regression analysis of the experimental data.

Methods for the Calculation of Unsteady-State Thermal Conditions of Isothermal Space Objects

A mathematical model is given, which describes unsteady-state thermal conditions of isothermal space objects (SO) of a convex shape. Calculations are performed of the surface-average temperature of SOs with a high thermal conductivity or of fast-rotating objects. Numerical results are obtained, as well as an approximate analytical solution which enables one to calculate the unsteady-state temperature of an SO having a sheath. The mathematical model has a general form for an SO of an arbitrary shape moving along a trajectory at a constant or variable distance from the Earth center. The first calculations are performed for an object of a spherical shape moving along a parabolic ballistic trajectory both at a preassigned angle of irradiation from the Sun and in the shadow of the Earth.

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].