Papers by Keyword: Phase Diagram

Abstract: We have investigated the magnetism and superconductivity of the electron-doped Eu_2-xCe_xCuO_4+α-δ in a wide range area of doping Ce⁴⁺ at 0.09 ≤ x ≤ 0.20 by means of magnetic susceptibility measurement at low temperatures down to 2 K. Superconductivity was observed in the concentration of Ce⁴⁺ at 0.12 ≤ x ≤ 0.20 with the range of the reduction of oxygen content 0.0255 ≤ δ ≤ 0.093 with a maximum transition temperature of 12 K. Furthermore, from the data temperature dependence of the dc magnetic-susceptibility, it can be analyzed the Curie constant, atomic magnetic moment and effective magnetic moment in each sample. Those three values have similar values with increasing Ce⁴⁺ concentration for a sample that doesn’t show superconductivity.

Abstract: An algorithm is proposed for constructing curves of thermal cooling and ordering kinetics with a monotonic decrease in temperature for alloys to stoichiometric composition. Modeling is carried out by the Monte Carlo method in the model of a rigid crystal lattice and pair interatomic interactions. The application of the algorithm is illustrated by the example to a square lattice, taking into account interatomic interactions in the first two coordination spheres for alloys with the composition AB, A3B, and A3B5. The proposed model makes it possible to calculate individual sections of the phase diagrams to the state for binary alloys.

Abstract: Heusler alloys have been considered as one of the most promising thermoelectric materials for electrical power generation in a temperature range of 500–800 °C. Establishment of phase diagrams allows one to predict formation, equilibria, and stability of phases in of these ternary alloys. In this work we report on the simulation and investigation of phase diagram and phase equilibria in ternary Ti-Fe-Sb system which is of considerable interest for thermoelectric applications. The simulation was carried out using the CALPHAD method in Pandat software. The existence of the thermoelectric Heusler TiFe_1.5Sb phase was revealed in a temperature range from 970 to 1070 K. The equilibria between TiFe_1.5Sb and other phases were determined. The entropy of formation was calculated for the phases existing at 970, 1020 and 1070 K using a fitting approach. A narrow equilibrium region containing pure body centered cubic Fe and TiFe_1.5Sb was found.

Abstract: Magnetic films, in which magnetic vortex textures - skyrmions appear because of competition between the direct Heisenberg exchange and the Dzyaloshinskii-Moriya interaction, were studied using the Monte-Carlo simulation technique. The conditions for the nucleation and stable existence of magnetic skyrmions in magnetic films in the frame of the classical Heisenberg model were considered in the paper. The process of nucleation of skyrmions with increasing of the external magnetic field was studied, various phases into which the Heisenberg spin system passes were recognized. A phase diagram was plotted: it shows the behavior of the system at the constant value of temperature depending on values of an external magnetic field and Dzyaloshinskii-Moriya interaction.

Abstract: A thermodynamic evaluation of the binary LaCl₃-CaCl₂ system was carried out by using CALPHAD method. The Modified Quasihelical Model was defined in order to describe the Gibbs energies of the liquid phases, and the model parameters were optimized from the experimental thermodynamic and phase diagram data. The phase diagram and the enthalpy of mixing of LaCl₃-CaCl₂ liquid were calculated. For LaCl₃-CaCl₂, a calculated eutectic point was observed at 924.82 K, 34.8 mol. % LaCl₃. The calculated enthalpy of mixing is exothermic, the minimum was found at approximately 30 mol. % LaCl₃. The thermodynamic properties and the phase diagram calculated from the optimized parameters agree well with the experimental data.

Abstract: The isothermal section at 800°C of the phase diagram of the ternary system Sc–Cu–Al was constructed in the whole concentration range using X-ray powder diffraction data. The existence of eight ternary compounds was confirmed: ScCu_4.9‑6.0Al_7.1‑6.0 (structure type ThMn₁₂, Pearson symbol tI26, space group I4/mmm), Sc₆Cu_24.1Al_11.9 (own structure type, cI176, Im-3), Sc₂Cu_6.25Al_4.75 (own structure type, oS108, Cmmm), Sc₃Cu_7.5Al_7.5 (Sc₃Ni₁₁Ge₄, hP38, P6₃/mmc), ScCu₂Al (MnCu₂Al, cF16, Fm-3m), ScCu_0.8Al_0.2 (CsCl, cP2, Pm-3m), ScCu_0.6Al_1.4 (MgNi₂, hP24, P6₃/mmc), and ScCuAl (MgZn₂, hP12, P6₃/mmc), and the existence of a continuous solid solution ScCu_1-xAl_x (x = 0-1), based on the binary compounds ScCu and ScAl with CsCl-type structure (cP2, Pm-3m), was established. The investigation of the Ti–Cu–Al system at 800°C confirmed the existence of four ternary compounds: TiCu_0.25Al_2.75 (ZrAl₃, tI16, I4/mmm), TiCu_0.3-0.6Al_2.7-2.4 (Cu₃Au, cP4, Pm-3m), TiCu_2-2.7Al_1-0.3 (MnCu₂Al, cF16, Fm-3m), and TiCu_0.54-1.16Al_l.46-0.84 (MgZn₂, hP12, P6₃/mmc). Electrical resistivity measurements were performed for three compounds in the Sc–Cu–Al system and confirmed metal behavior in the temperature range 5-290 K.

Abstract: The phase equilibria in the ternary systems {Ce, Gd}–{Ti, Zr}–Sb were investigated by means of X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The isothermal sections of the phase diagrams at 600°C were constructed. The formation of three ternary compounds (Ce₂Ti₇Sb₁₂, Ce₃TiSb₅, and Gd₂Ti₁₁Sb₁₄) was confirmed in the {Ce, Gd}–Ti–Sb systems and no more ternaries were found. The investigation of the {Ce, Gd}–Zr–Sb systems revealed several new ternary compounds and confirmed the known ones. The crystal structure of the new compound Ce_0.08(3)Zr_1.92(3)Sb was determined from X-ray powder diffraction data. The other new compounds in the Ce–Zr–Sb system were found to have compositions close to ~CeZrSb₄ and ~Ce₂Zr₃Sb₅. In the Gd–Zr–Sb system the existence of a large homogeneity range was established for the GdZrSb compound along the isoconcentrate 33.3 at.% Sb: Gd_1-xZr_1+xSb (x = 00.905(18) at 600°C), and a new compound, ~Gd₃Zr₃Sb₁₄, was discovered. The crystal structures at the boundary compositions of the Gd_1-xZr_1+xSb phase were refined from X-ray powder diffraction data.

Abstract: Previous researchers have proved that units constituting monodisperse bilayer foams can transform reversibly by changing foam liquid fraction. Structural transformation of bilayer ferro-foams caused by magnetic field is investigated in this paper. It is observed that bilayer ferro-foams transform from Tóth structure to honeycomb structure caused by liquid fraction change which attributes to foam imbibition under a uniform magnetic gradient field. In order to acquire critical structural transformation liquid fraction range, foam liquid fractions are calculated by image analysis. However, we also observed that, when applying a homogeneous magnetic field, bilayer ferro-foams can also perform this transformation at a constant liquid fraction. This phenomenon is related to energy absorption of foam system, which is induced by magnetic interaction of magnetic moments after applying a magnetic field. This self-organizational behavior of foam structure is believed to be based on energy minimization principle. This study opens possible applications in the field of metal foam preparation.

Abstract: In this work we discussed the modeling of the demixing curve in the liquid state in the Lead – Zinc binary system. We are interested to recalculate the free energies relating on Pb-Zn alloys for several temperatures based on the thermodynamic data collected in the bibliography. This calculation allows us to trace the curve of phase separation from a program after obtaining the mole fractions corresponding to the common tangent to the curve of the free energy with two minima at different temperatures. To do this, we used the Matlab 7.1 as the programming language and the Redlich-Kister polynomial as a mathematical model of development. The results obtained are very satisfactory by comparing them with those of the bibliography.

Abstract: Most aluminum alloys used in industrial manufacturing are multi-component systems. Unfortunately, multi-component systems are still lack of systematic research. The lack of research is especially evident for the liquidus surface projection of the multi-component system where most of the projections are currently drawn by hand. Thermodynamic calculations were performed for the Al–Cu–Mg–Mn quaternary system and the A1–Cu–Fe–Mg–Mn quinary system. The temperatures and compositions of the liquidus invariant reactions in the A1–rich corner for the two systems were calculated and compared with the experimental data. The current work provides a straightforward and accurate expression for the liquidus surface projections of multi-component systems. The expressions will facilitate the understanding of the multi-component alloy systems that are frequently used in industrial applications.