Synthesis of Lower Oxides of Transition Metals from Chloride Melts

Synthesis of transition metal oxides MO₂ (M^{I V} = Mo, W, or Nb) and V₆O_{1 3} in alkali chloride melts and their crystallographic characteristics are described. The advantages of the proposed technology are demonstrated. The thermodynamic parameters of the proposed reactions are calculated.     

Thermodynamic properties of liquid alloys Ni-Eu and Ni-Yb

Mixing enthalpies of melts of the binary Ni-Eu (0 < x _Ni < 0.89) and Ni-Yb (0 < x _Ni < 1) systems at 1300–1750 K were investigated using the isoperibolic calorimetry. They have alternating signs depending on the melt concentration. With the combined analysis of the data determined by us and in literature, the models of the liquid and solid alloys were obtained, and the phase diagrams were calculated.     

Thermodynamic Properties of Alloys of the Sn–Yb System

Thermochemical properties of liquid alloys of the Sn–Yb system are studied via calorimetry at 1110–1310 K over the ranges of concentrations 0 < x_Yb < 0.47 and 0.82 < x_Yb < 1. Considerable negative heat effects of the mixing of these alloys are identified. Activities of the components, the Gibbs energies and entropies of mixing, and the liquidus curve of the phase diagram of this system are calculated using the ideal associated solution (IAS) model and agree with data from the literature.     

The thermodynamic characteristics of formation of alloys in the Ge-Ga-Mn and Si-Ni-Al systems

The enthalpies of mixing of ternary system melts were determined by high-temperature calorimetry under isoperibolic conditions. For the Ge-Ga-Mn system, measurements were taken at 1780 ± 5 K along five ray sections with constant ratios between the atomic fractions of germanium and gallium up to a ～0.6 mole fraction of manganese; the x _Ge/x _Ga ratios were 0.8/0.2, 0.7/0.3, 0.5/0.5, 0.3/0.7, and 0.15/0.85. For the Si-Ni-Al system, measurements were taken at 1770 ± 5 K along five ray sections with constant ratios between the atomic fractions of silicon and nickel up to a ～0.6 mole fraction of aluminum; the x _Si/x _Ni fratios were 0.85/0.15, 0.7/0.3, 0.5/0.5, 0.3/0.7, and 0.15/0.85. The formation of melts in these systems was found to be exothermic over the composition range studied. The integral enthalpies of melt formation were maximum along the x _Ge/x _Ga = 0.8/0.2 section in the Ge-Ga-Mn system (?18.8 ± 3.3 kJ/mol) and along the x _Si/x _Ni = 0.5/0.5 section in the Si-Ni-Al system (?67.8 ± 3.4 kJ/mol). An analysis of the isolines of the integral enthalpies of mixing led us to conclude that the Ge-Mn and Ga-Mn binary systems had the strongest influence on the thermodynamic characteristics of melt formation in the Ge-Ga-Mn system, the predominant influence being that of the Ge-Mn binary system. An analysis of the energy characteristics of melt formation in the Si-Ni-Al ternary system showed that the major contribution was made by the interaction of components in the Si-Ni and Ni-Al boundary binary systems, the influence of the Si-Ni system being stronger.     

Thermodynamic properties of melts of Mn-Sc(Y, Ln) systems

Partial and integral mixing enthalpies of melts of binary systems Mn-Sc and Mn-Y at 1873 and 1830 K, respectively, are determined by calorimetry. It is found that the minima of the mixing enthalpies are ?7.1 ± 0.4 and -3.2 ± 0.2 kJ/mol at x _Mn = 0.60 and 0.61, respectively. The initial partial mixing enthalpies of Sc and Y are ?33.2 ± 2.1 and ?16.6 ± 0.8 kJ/mol, respectively. The thermodynamic properties of melts of binary Mn-Sc(Y) systems are calculated using the ideal associated solution (IAS) model. It is found that the activities of the components exhibit slight negative deviations from the ideal solutions, and the excess Gibbs energies reach ?3.0 and ?1.6 kJ/mol, respectively.     

Elastic Equilibrium of Circumferentially Inhomogeneous Orthotropic Cylindrical Shells of Arbitrary Thickness

An approach is proposed to determine the three-dimensional stress–strain state of hollow orthotropic cylinders with elastic characteristics variable in the circumferential direction. The solution of the problem is represented as a double Fourier series in the axial and circumferential coordinates. A resolving system of ordinary differential equations of high order is derived. An analysis is made of the stress state of a cylinder made of a composite with reinforcement density variable in the circumferential direction     

Phase relations in the system K2MoO4–KPO3–MoO3–Bi2O3: A new phosphate K3Bi5(PO4)6

Phase equilibrium in the pseudo-quaternary system K₂O–MoO₃–P₂O₅–Bi₂O₃ was studied as three-component solvent K₂MoO₄–KPO₃–MoO₃ containing 15 mol% Bi₂O₃ during slow cooling and spontaneous crystallization. The results of the investigation were shown on a composition diagram, which indicates the crystallization fields of K₂Bi(PO₄)(MoO₄), K₅Bi(MoO₄)₄, BiPO₄ and K₃Bi₅(PO₄)₆. New phosphate K₃Bi₅(PO₄)₆ was characterized by single-crystal X-ray diffraction (space group C2/c, a=17.680(4), b=6.9370(14), c=18.700(4) Å, β=113.79(3)°) and FTIR spectroscopy. The possibility of lone electron pair stereoactivity of bismuth was suggested using the calculations of characteristics of the Voronoi–Dirichlet polyhedra for K₃Bi₅(PO₄)₆ and K₂Bi(PO₄)(MoO₄).