Density inversions between fluid and solid phases in the system HeH2 at high pressures

One of the well-known interesting features of the helium—hydrogen system is the occurence of the barotropic phenomenon: the density inversion between the gaseous and the liquid phase. However, density inversions between the liquid and the solid phases of mixtures (if the pure solids are more dense than the pure liquids) have not been observed experimentally. Such inversions may be of importance in modelling the atmosphere of the planets. In this paper results are presented concerning the measurements of the relative density of gaseous, liquid and solid phases in several types of phase equilibria in the system helium—hydrogen.     

An investigation of the polythermal diagram of the H2ONa2HPO4Na2SO4 system

The polythermal diagram of the ternary system H₂ONa₂HPO₄Na₂SO₄ has been established, setting up nine isotherms obtained between 0 and 25°C by conductimetric analysis. The solubility domains of the various solid phases have been determined. One eutectic, three stable and one metastable transitional transformations have been observed. Temperature and composition of the eutectic point have been obtained by thermal analysis at constant flow.     

X-ray study of the system ThO2CeO2Ce2O3

The mixed oxide system ThO₂CeO₂Ce₂O₃ was investigated using X-ray powder techniques. ThO₂ forms a complete range of solid ssolutions with CeO₂, the solid solutions having a fluorite structure. Reduction of mixed crystals of (ThCe)O₂ at temperatures in the range 700–1400°C with pure, dry hydrogen yields a single phase (ThCe)O_2−x wich has a fluorite structure for values of x less than 0·25. X-ray powder photographs of (ThCe)O_2−x in which x is greater than 0·25 showed extra lines which may be indexed in terms of a body centred cubic structure with a = 2a₀ (fluorite). In vacuo density measurements on the reduced solid solutions showed them to have an anion vacancy structure.     

Thermodynamics of the URuC system

Thermodynamic measurements by the electromotive force method were made on the binary intermetallic phases URu₃ and U₃Ru₅ and on the ternary carbides URu₃C_0.7 and U₂RuC₂ of the URu and the URuC systems between 950 and 1200 K using galvanic cells with CaF₂ single crystal electrolytes: U, UF₃¦CaF₂¦UF₃, URu₃, Ru; U, UF₃¦CaF₂¦UF₃, U₃Ru₅, URu₃; Ru, URu₃, UF₃¦CaF₂¦UF₃, URu₃C_0.7, Ru, C; U, UF₃¦CaF₂¦UF₃, URu₃C_0.7, U₂RuC₂, C. The Gibbs energies of formation of URu₃, U₃Ru₅, URu₃C_0.7 and U₂RuC₂ were evaluated from the measured electromotive force which give ^fΔG^o〈URu₃〉 = −199 100 + 35.9 T J mol^−1fΔG^o〈U₃Ru₅〉 = −398 600 + 43.6 T J mol^−1fΔG^o〈URu₃C_0.7〉 = −192 600 + 2.5 T J mol^−1fΔG^o〈U₂RuC₂〉 = −380 200 + 52.5 T J mol⁻¹ The implications of these thermodynamic data for the behaviour of the fission product ruthenium in irradiated carbide fuels are discussed.     

Phase equilibria of the Ag2OTeO2V2O5 system

The phase diagram Ag₂OV₂O₅TeO₃ is studied in the region rich in TeO₂ with the aid of DTA and X-ray analysis. It is found that the sections TeO₂Ag₂O.V₂O₅.2TeO₂ and Ag₂O.TeO₂Ag₂O.V₂O₅.2TeO₂ are simple ones. A new compound with a composition of Ag₂O.3V₂O₅.6TeO₂ has been found in the section 2TeO₂.V₂O₅Ag₂O.V₂O₅.2TeO₂ which melts incongruently. A part of the liquidus diagram of the system in which the two ternary compounds participate is plotted.     

On the uranates of ammonium—II: X-ray investigation of the compounds in the system NH3UO3H2O

The X-ray powder diagrams of four compounds in the system NH₃UO₃H₂O have been indexed. The following results were obtained:

• 1.I: β-UO₃·2H₂O; orthorhombic; a = 13·977 ± 0·004 Å; b = 16·696 ± 0·004 Å; c = 14·672 ± 0·004 Å.
• 2.II: 3UO₃·NH₃·5H₂O; orthorhombic; a = 7·220 ± 0·003 Å; b = 12·198 ± 0·003 Å; c = 15·072 ± 0·004 Å.
• 3.III: 2UO₃·NH₃·3H₂O; hexagonal; a = 14·087 ± 0·004 Å; c = 14·494 ± 0·005 Å;
• 4.IV: 3UO₃·2NH₃·4H₂O; hexagonal; a = 4·031 ± 0·004 Å; c = 14·58 ± 0·001 Å

.The structures consist of hexagonal or pseudohexagonal layers of composition UO₂(O₂)_∞, with the additional O and N atoms of water and ammonia between these layers.     

Phase equilibrium diagram of the system MnCrO

A hypothetical oxygen pressure-composition phase diagram and a projection of the oxygen pressure-temperature-composition diagram on the composition triangle were constructed from phase equilibria in the system MnCrO on the basis of the data available in literature. The temperature-composition phase equilibrium diagram of this same system in air was specified. Isomorphism of solid solutions with spinel and hausmannite structure and their intertransformation was studied. Two chemical compounds, MnCr₂O₄ and Cr₄Mn₂₈O₄₈, are supposed to exist in the system.     

Reinvestigation of phase relations in the CaOUO2 system

Phase relationships in the binary CaOUO₂ system were reinvestigated. In a carefully controlled reducing atmosphere the formation of binary compounds was not detected and only extensive solid solubility of CaO in UO₂ was observed. In controlled atmosphere in wet hydrogen, a perovskite, Ca₂ (Ca_0.67U⁴⁺_0.33)U⁵⁺O_5.83 is formed as the single binary Ca compound containing uranium in a 4+ valence state.     

Investigation of the CeFe binary system

The CeFe binary system was investigated and an FeCe binary phase diagram was proposed. This system consists of

• 1.(i) two peritectic reactions, γ-Fe + L → Ce₂Fe₁₇ and Ce₂Fe₁₇ + L → CeFe₂, occurring isothermally at 1063°C and 925°C respectively;
• 2.(ii) a eutectic reaction, L → CeFe₂ + Ce, occurring isothermally at 592°C with eutectic containing 83.3 at.% Ce (92.6 wt.% Ce);
• 3.(iii) a peritectoid reaction, γ-Fe + Ce₂Fe₁₇ → α-Fe(Ce), occurring isothermally at 922 °C.

The solid solubility of cerium in iron in the temperature range 850–900 °C was found to be less than 0.04 at.% (0.1 wt.%). The Curie temperature of α-Fe(Ce) was slightly lowered with increasing cerium content in solid solution.     

Phase investigations of the AlIr system

The phase behavior of the AlIr system has been studied using differential thermal analysis, electron microprobe analysis, X-ray diffraction, chemical analysis and X-ray fluorescence. Our work confirms the existence of four compounds: Al₉Ir₂, Al₃Ir, Al_2.7Ir and AlIr. We also observed an additional intermetallic phase, with a stoichiometry corresponding to Al₁₃Ir₄; however, this compound exhibits a complex X-ray pattern and currently no structure has been determined.Peritectic temperatures were determined for Al₉Ir₂ (900 °C), Al₁₃Ir₄ (1015 °C) and Al₃Ir (1450 °C). The Al_2.7Ir phase is stable to above 1450 °C, and the congruent melting temperature of AlIr is 2120 ± 20 °C. The solubility of aluminum in iridium was measured between 1085 and 1850 °C, and the maximum solid solubility was extrapolated to 18 at.% at 2058 °C. The maximum solid solubility of iridium in aluminum was measured to be less than 0.1 at.%. A phase diagram for the AlIr system is presented.     

The devitrification of glasses in the binary system SiO2TiO2

The solid solutions series in the system SiO₂TiOP₂ in the vitreous as well as in the devitrified state were investigated by various methods up to 10% by weight TiO₂. The relative intensities of the characteristics infrared absorption bands and of the respective Raman scattering bands about 950 cm⁻¹ reach their maximum at about 4% TiO₂ (by weight).These and other effects observed at this concentration of TiO₂ are discussed in connection with the linking of [SiO₄] and [TiO₄] tetrahedra and with the observed separation of rutile and anatase in small quantities in the devitrification process. A possible sequence of events during the devitrification process in this system is suggested.     

The system UO2(NO3)2UO3H2O

The phase diagram of the system UO₂(NO₃)₂UO₃H₂O at 25°C has been determined. Only three solid phases have been found in this system: UO₂(NO₃)₂·6H₂O, UO₃·2H₂O and a metastable basic uranyl nitrate. The phase UO₃·2H₂O exhibits a pronounced solubility in this system.     

Solid-phase equilibria in the system NiOMn2O3O2

A complete phase diagram is presented for the system NiOMn₂O₃O₂ showing the phases which can exist in the air or pure oxygen at temperatures between 600 and 1200°C. Six phases are observed: rock-salt phase Ni_1−sMn_s O ≤ s ≤ 0·025), an ordered rock-salt phase Ni₆MnO₈, an ilmenite phase Ni_2−pMn_pO₃ (1 ≤ p ≤ 1·06), a cubic spinel phase Ni₃−yMn_yO₄ (1·725 ≤ y ≤ 3·000), a tetragonal spinel phase Ni_3−yMn_yO₄ (2·895 ≤ y ≤ 3·000) and a C-rare-earth-oxide or α-Mn₂O₃ phase Mn_2−zNi_zO₃ (O ≤ z ≤ 0·230). Argument is drawn to show that all the phases except the simple rock-salt probably contain manganese in the +4 oxidation state.     

Liquid-liquid extraction model for the system LaCl3Nd(NO3)3HNO3H2OHDEHP-AMSCO

The liquid-liquid extraction model for a binary metal system successfully applied to the lanthanide nitrate system was found to be applicable to the binary metal-mixed ligand system only when equal mole fractions of each metal components are present in the feed solution. The agreement in this special case is explained satisfactorily in terms of the two-suffix Margules equations. The lack of agreement between the chemically based model and the experimental data was attributed to the effects of the stability constants and the degree of formation of the lanthanide mixed ligand complexes on the separation factors.