R. A. Khairulin

Phase transitions and thermal properties of gadolinium trifluoride

Abstract The temperature dependence of gadolinium trifluoride density in the solid and liquid states was determined by a gamma attenuation technique. Volume changes on solid–solid and solid–liquid transitions were measured. The density and volume coefficient of thermal expansion of the liquid salt at the melting point are equal to 5609±25 kg m −3 and (16.2±0.5)×10 −5 K −1 , respectively. The relative density reduction on melting equals 16.7±0.15%. The polymorphic transformation from the low-temperature orthorhombic modification (a lattice of β-YF 3 type) into the high-temperature hexagonal phase (LaF 3 type) occurs with an increase of the density (about 2.1%). The peculiarities of the thermal expansion of the solid rare earth fluorides, undergoing phase transition β-YF 3 -type→LaF 3 -type, are discussed.

Study of the binary diffusion in liquid Sn–Pb and Al–Ge alloys by measurement of the melt concentration

Abstract A new method for the measurement of the coefficients of mutual diffusion in binary melts is described. The technique is based on immediate investigation of the evolution of composition profile with time in inhomogeneous liquid samples. The concentration is determined from measurement of the attenuation of the γ radiation in the melt. Diffusion factors of liquid alloys of tin–lead (50 at.% Pb) over the temperature range from 730 to 1030 K, and of aluminium–germanium (28.5 at.% Ge) at 1250 K were determined by this method. A comparison of the results obtained for the Sn–Pb system with literature data confirms the reliability of the proposed technique.

Studies of the thermophysical properties of substances and materials at the Novosibirsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences, 2002–2012

This review contains the results of theoretical and experimental studies performed by the thermo-physicists of the Novosibirsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences over the last ten years. The problems of constructing the wide-range equations of state that take into account the singular behavior of thermodynamic functions in the critical region are considered, and new experimental data on the thermodynamic and transport properties of refrigerants and low-melting alloys, including alloys used as heat-transfer agents in the nuclear energy industry, are reviewed. A complete bibliography of the published papers, first of all, from the journal High Temperatures is given.

THE DENSITY AND THERMAL EXPANSION OF EUTECTIC ALLOYS OF LEAD WITH BISMUTH AND LITHIUM IN CONDENSED STATE

The method of penetrating gamma-radiation is used to measure the density of lead-bismuth and lead-lithium eutectics in the condensed state in the range from room temperature to ~1250 K. The chemical composition of investigated eutectic alloys of Pb-Bi and Pb-Li systems is determined within ±0.2% by mass, and the lead content in these alloys turns out to be 44.6 and 99.3% by mass, respectively. The confidence error of the experimental results, which combines the systematic and random components, does not exceed 0.3% and 0.2% for the solid and liquid phases, respectively. The investigation results are compared with the available literature data on the density of eutectic alloys of lead with bismuth and lithium in the condensed state.

Experimental study of density and thermal expansion of the advanced materials and heat transfer agents for liquid metal systems of thermonuclear reactor: Lithium

Using the gamma-ray attenuation technique, the density of the condensed state of lithium is measured within the range from room temperature up to ∼700 K. The purity of the investigated lithium is as high as 99.95 mass %. The confidence error of experiments is within 0.3%. From the experimental results, the volume thermal expansion coefficient of lithium is calculated within a wide temperature interval. The experimental data obtained on thermal properties of the solid and liquid state of lithium are compared to those available in the literature.

The density and interdiffusion coefficients of bismuth-tin melts of eutectic and near-eutectic composition

The method of gamma-raying of samples by a narrow beam of gamma radiation is used to investigate the temperature dependences of the density of bismuth-tin liquid alloys, which contain 30.0, 44.0, and 54.0 at.% Bi, at temperatures from the liquidus line to 920 K. The density jump in the case of solid-liquid phase transition is directly measured for the first time for an alloy of eutectic composition (44.0 at.% Bi). The temperature and concentration dependences of the thermal properties of the liquid Bi-Sn system are constructed. The kinetics of homogenization are studied of melts with average composition of 44.0 and 54.0 at.% Bi at temperatures from 550 to 850 K. The interdiffusion coefficients are determined from the results of these experiments.

Liquid-liquid equilibrium in the-n-heptane-n-perfluorohexane system

The shape of the liquid-liquid coexistence curve in the C7H16-C6F14 system in the molar concentration-temperature coordinates close to the critical solution point was studied by narrow-beam gamma-raying of two-phase samples. The molar volumes of the coexisting liquid phases and critical point coordinates (critical temperature Tc = 316.266 ± 0.03 K and critical concentration xc = 39.0 ± 0.4 mol % C6F14) were determined. The critical index β of the coexistence curve was found to be 0.322 ± 0.005. The diameter of the coexistence curve did not obey the classic “rectilinear diameter rule.”

Density changes of ytterbium trifluoride on phase transitions

Abstract The density and thermal expansion of the melt and high-temperature solid phase of YbF3 were studied by a gamma attenuation method. Volume changes on melting and on polymorphic transformation were measured. The density and volume coefficient of the thermal expansion of the liquid at the melting point are equal to 6284 kg m−3 and 14.7 × 10−5 K−1. Relative density changes on melting and on solid-solid transition are equal to 2.6% and 16.6%, respectively.

“Chemical contraction” in rubidium–bismuth melts

The density and thermal expansion of liquid rubidium and rubidium–bismuth alloy containing 25.0 at % Bi were measured by the gamma-ray attenuation technique at temperatures from liquidus to 1000 K. The results of this study were compared with the data obtained by other authors. The molar volume of the Rb75Bi25 melt strongly deviates from the additivity rule for ideal solutions.

Crystallization and thermal properties of rare earth gallium garnets

Abstract The density and thermal expansion of a number of rare earth gallium garnets were studied in the liquid and solid states in the regions of crystallization and melting by irradiating the samples with a narrow beam of gamma quanta. Volume changes on liquid-solid and solid-solid transitions were measured for equilibrium and nonequilibrium crystallization. The formulas for the estimation of the thermal properties of the liquid rare earth gallium garnets remaining to be explored were obtained.