Reinvestigation of Phase Equilibria in the V2O5–ZnO System

A diagram of phase equilibria established in a two-component oxide system V_{2 5}–ZnO has been worked out applying differential thermal analysis and X-ray phase analysis as well as depending on investigations carried out with the aid of high-temperature X-ray attachment and scanning electron microscope linked to an X-ray microanalyser. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phase Equilibria in the System Fe2O3–V2O5 –WO3 in the Solid State

DTA and X-ray phase diffraction methods were used to construct a solidus area projection onto the component concentration triangle plane of the system Fe₂ O₃-V₂ O₅-WO₃. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phase Equilibria in The System La2O3–K2O–P2O5

The ternary system La₂O₃–K₂O–P₂O₅ has been examined by thermal, X-ray, IR and microscopic methods. The existence of three double potassium-lanthanum phosphates, K₃La(PO₄)₂, KLa(PO₃)₄ and K₂La(PO₃)₅ has been confirmed, and the phase diagram of the ternary system La₂O₃–K₂O–P₂O₅ over the composition range LaPO₄–K₃PO₄–P₂O₅ has been determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phase Equilibria in the Ni–Al–W System at 900°C

Summary. Multicomponent Ni-base alloys exhibit good mechanical properties even at elevated temperatures and they are widely used for industrial production of exertion-resistive parts of engines. These properties are mainly determined by the coexistence of a disordered γ matrix with a face centred cubic lattice and cuboidal domains of its ordered γ′ structure. Therefore it is useful to study phase equilibria in Ni-base systems, namely in the regions involving both mentioned phases. One of the conclusions of our recent work on Ni–Al–Cr–W system was a necessity of modification of selected thermodynamic parameters of the ternary Ni–Al–W subsystem in order to achieve a better agreement of our experimental observations with theoretical modelling. This involves new measurements of the microstructure of selected samples of the Ni–Al–W system at 900°C and the comparison of the results with existing literature data in order to confirm our conclusions on higher order system investigated before. It is a first step on the way to an assessment of the Ni–Al–W system, which has not been done before.     

Electric Conductivity of Glasses in the MgO–V2O5–P2O5 System

Russian Journal of Electrochemistry - Amorphous glasses of the composition xMgO–yP2O5– (100 – x – y)V2O5 with x = 1–5 and y = 5, 10, and 15 mol % are obtained by the...     

Synthesis and Properties of The Solid Solutions Formed in The Fe2V4O13–Cr2V4O13 System

DTA and XRD studies of the Fe₂V₄O₁₃–Cr₂V₄ O₁₃ system have shown that continuous solid solutions of a Fe_2–xCr_xV₄O₁₃ type, bearing a Fe₂ V₄ O₁₃ structure, are formed in the system. With the increasing degree of the Cr3+ ion incorporation into the Fe₂ V₄ O₁₃ structure, a contraction of the solid solution crystal lattice develops. Solid solutions of a Fe_2–x Cr_x V₄ O₁₃ type melt incongruently, their melting temperature increasing from 953 to 1003 K with increase in the degree of the Cr³⁺ ion incorporation. The solid product of melting Fe_2–x Cr_x V₄ O₁₃ solid solutions for 0.2<x >1.2 is the Fe_1–x Cr_x VO₄ solution phase, and for x ≤0.2 and x ≥1.4 – the Fe_1–x Cr_x VO₄ phase as well as FeVO₄ or CrVO₄ , respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phases in the subsolidus area of the system CuO–V2O5–Fe2O3

The phase equilibria in the solid state in the system FeVO₄?CCu₃V₂O₈ and FeVO₄?CCuO have been determined. Based on the obtained DTA and XRD analysis results and some additional research, a phase diagram in the whole subsolidus area of the system CuO?CV₂O₅?CFe₂O₃ has been worked out. Eighteen subsidiary subsystems can be distinguished in this ternary system. Basic properties of the obtained phases with howardevansite- and lyonsite-type structure have been investigated by DTA, IR, and SEM methods.     

Reactivity in Air of SbVO5 Towards MoO3 and Phase Equilibria in the SbVO5–MoO3 System in the Solid State

The use of XRD and DTA methods has allowed studies on the interaction of the SbVO₅ and MoO₃, taking place in the solid state and in the medium of ambient air. The experimental results of XRD and DTA for all the samples showed the presence of a novel phase, i.e. Sb₃V₂Mo₃O₂₁ apart from various amounts of MoO₃ and V₉Mo₆O₄₀ or SbVO₅ and V₂O_5(s.s.). The SbVO₅–MoO₃ system is not a real two-component system over the entire range of component concentrations up to the solidus line. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study on Phase Relations in Zn3V2O8–ZnMoO4 System

The phase equlibria established in the Zn₃V₂O₈–ZnMoO₄ system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed using the results of DTA and XRD methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Catalytic Properties of the Fe2O3–Bi2O3 System in Ammonia Oxidation to Nitrogen Oxides

The catalytic properties of the Fe₂O₃–Bi₂O₃ system in ammonia oxidation are studied at 1073 K. The effect of phase composition on the physicochemical and catalytic properties of the system is determined. The catalytic properties of individual components of the system (-Fe₂O₃, Bi₂Fe₄O₉, BiFeO₃, and -Bi₂O₃) are studied.     

Phase Equilibria and Crystal Structure of Complex Oxides in the La–Sr–Co–Ni– System

Phase equilibria in the La–Sr–Co–Ni–O system were studied in air at 1100°. The samples for the study were synthesized by the standard ceramic and citrate processes. The limiting solubility and structure of La_1-xSr_xCo_1-yNi_yO_3- and (La_1-xSr_x)₂Co_1-yNi_yO₄ solid solutions were determined by Xray powder diffraction analysis. La_1-xSr_xCo_1-yNi_yO₃- solid solutions with 0 x 0.5 have a distorted rhombohedral perovskitelike structure (R c space group). An increase in the strontium concentration reduces the rhombohedral distortions, and the compounds with x < 0.5 have an ideal cubic structure (Pm3m space group). (La_1-xSr_x)₂Co_1-yNi_yO₄ crystals have a tetragonal K₂NiF₄ type unit cell (I4/mmm space group). The relationships between unit cell parameters and compositions were obtained for singlephase La_1-xSr_xCo_1-yNi_yO_3- and (La_1-xSr_x)₂Co_1-yNi_yO₄ samples. The existence regions of La_1-xSr_xCo_1-yNi_yO₃- and La_1-xSr_x)₂Co_1-yNi_yO₄ solid solutions were distinguished on P–T phase diagrams.     

Synthesis and structural investigation of a unique columnar phase in the Bi2O3–TeO2–V2O5 System

A new columnar phase Bi(11.65)Te(1.35)V(5)O(34-δ) (δ ～ 1.3) containing VO(4) tetrahedra has been identified for the first time in the Bi(2)O(3)-TeO(2)-V(2)O(5) system. The phase formation and the extent of substitution of Te(4+) for Bi(3+) ions in order to stabilize V(5+) in this composition have been confirmed by the single crystal analysis, combined with the powder X-ray diffraction of the solid state synthesized bulk crystalline samples. The oxide crystallizes in a monoclinic crystal system, space group P2/c, with unit cell parameters a = 11.4616(7) ?, b = 5.7131(3) ?, c = 23.5090(18) ?, β = 101.071° (6) (Z = 2). The structure retains the basic features of the columnar oxides with the presence of [Bi(10.65)Te(1.35)O(14)](n)(9.35n+) columns along the (010) direction, surrounded by (VO(4)) tetrahedra placed in the planes parallel to (100) and (001), with an isolated bismuth atom in between the columns. The composition with a limited Te(4+) substitution, Bi(11.65)Te(1.35)V(5)O(34-δ) (δ ～ 1.3), exists with a surprisingly high oxygen deficiency as compared to the stoichiometrically known columnar oxides such as Bi(13)Mo(4)VO(34), Bi(12)Te(1)Mo(3)V(2)O(34), and Bi(11)Te(2)Mo(2)V(3)O(34). The structure of this interesting member of the columnar family of oxides based on the single crystal X-ray diffraction and the Raman spectroscopic studies indicates the possibility of the distribution of the oxygen vacancies among the VO(4) tetrahedral units. Further confirmation for the formation of vanadium stabilized columnar structures has been provided by the successful preparation of Bi(11.65)Te(1.35)V(4)CrO(34-δ) (δ ～ 0.83) and Bi(11.65)Te(1.35)V(4)WO(34-δ) (δ ～ 0.83) phases. Preliminary investigation of the photocatalytic efficiencies of the oxides Bi(11.65)Te(1.35)V(5)O(34-δ), Bi(11.65)Te(1.35)V(4)CrO(34-δ), and Bi(11.65)Te(1.35)V(4)WO(34-δ) revealed moderate photocatalytic activities for the decomposition of the dyes such as Rhodamine B under UV-vis light irradiation.     

Thermodynamic Analysis of Phase Equilibria in the System Cyclohexane—Methanol

The phase diagram of cyclohexane-methanol was thermodynamically modeledin the range of 150 T/K 360 and at a pressure of 1 bar on the basis ofavailable experimental data. The Gibbs energy functions of four pure solid andtwo mixture phases were taken into consideration. The liquid phase was describedby a model based on mole fraction statistics and the simplified assumption ofmethanol tetramers mixed with cyclohexane monomers. The gas phase was treatedas a nonideal mixture with a Gibbs energy modeled on the basis of the virialcoefficient formalism considering only monomers. The Gibbs energies of the twosolid modifications of pure methanol, as well as pure cyclohexane, were fixedusing literature data. The pressure dependence of the Gibbs energies of the liquidand solid phases were neglected. The complete T-x phase diagram includinggas/liquid equilibria as well as p-x phase diagrams in the range of 20 and 55°C werecalculated. Experimental and calculated data were found to agree reasonably well.     

Comparative studies in subsolidus areas of ternary oxide systems PbO–V2O5–In2O3 and PbO–V2O5–Fe2O3

Thermal stability of PbO was studied. Reactivity of oxides in the systems PbO–M₂O₃ (M = In, Fe) was investigated up to 650 °C. Using the DTA and XRD methods, parts of investigated ternary oxide systems, labelled by compounds: V₂O₅, Pb₈V₂O₁₃ and M₂O₃ (M = In, Fe), have been divided into partial ternary systems. IR spectra of compounds Pb₂MV₃O₁₁ (M = In, Fe) have been compared.     

Phase Equilibria in the System NH4Al(SO4)2–H2SO4–H2O

Equilibrium solubility curves of the ammonium aluminium sulphate in aqueous solutions of sulphuric acid have been calculated using checked literature data and our own measurements. The concentration of sulphuric acid ranged from 0 to 23 mass%, temperature range between 20 and 60°C has been extrapolated up to 75°C by means of a thermodynamically based correlation method. The solubility correlation as well as the hydration analysis implied a possible destructuralization of solutions at higher acid concentrations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phase Relations in The System Al2(MoO4)3–V2O5

The phase equilibria established in the system Al₂ (MoO₄ )₃ –V₂ O₅ throughout the whole component concentration range up to 1000°C were investigated by DTA and XRD methods. The results are presented in the form of a phase diagram. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phase Equilibria in the Ag–In–Pd System at 700°C

Summary. Phase equilibria in the Ag–In–Pd system were determined at 700°C based on experimental results for 21 alloys. A ternary compound T₁ (with the approximate composition AgInPd₂) was identified by XRD analysis. These data were compared with the results of a CALPHAD-type prediction, based on binary thermodynamic data only and a symmetrical Redlich–Kister–Muggianu model. The experimental results will serve as a basis for refined thermodynamic modeling of the different phases in this ternary system.     

Rheological Properties of the Hydrated Al2O3–TiO2System

The rheology of mixtures of hydrated aluminum oxide and hydrated titanium dioxide sols was investigated. It was shown that flow curves depend on the mixture composition, the age of initial sols, the contact time of components, and the temperature. At low deformation rates, particles are aligned with the flow; this effect is partially reversible. At high shear rates, a discontinuity appears in the system; the effect depends on the age of initial sols.     

Phase Equilibria in the System YPO4–K3PO4–KMgPO4

The phase equilibria in the part of the ternary system YPO₄–K₃PO₄–Mg₃(PO₄)₂ over the composition range YPO₄–K₃PO₄–KMgPO₄ were examined and determined by differential thermal analysis, X-ray powder diffraction and microscopic analysis in reflected light. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaporation and Thermodynamic Properties of the CeO2–TiO2–ZrO2 System

Russian Journal of General Chemistry - The processes of the TiO2–CeO2–ZrO2 system evaporation were studied by high-temperature mass spectrometry. The values of the activities of TiO2...