Miscibility Gap Region Research Articles

Understanding How the Suppression of Insertion-Induced Phase Transitions Leads to Fast Charging in Nanoscale LixMoO2.

Fast-charging Li-ion batteries are technologically important for the electrification of transportation and the implementation of grid-scale storage, and additional fundamental understanding of high-rate insertion reactions is necessary to overcome current rate limitations. In particular, phase transformations during ion insertion have been hypothesized to slow charging. Nanoscale materials with modified transformation behavior often show much faster kinetics, but the mechanism for these changes and their specific contribution to fast-charging remain poorly understood. In this work, we combine operando synchrotron X-ray diffraction with electrochemical kinetics analyses to illustrate how nanoscale crystal size leads to suppression of first-order insertion-induced phase transitions and their negative kinetic effects in MoO2, a tunnel structure host material. In electrodes made with micrometer-scale particles, large first-order phase transitions during cycling lower capacity, slow charge storage, and decrease cycle life. In medium-sized nanoporous MoO2, the phase transitions remain first-order, but show a considerably smaller miscibility gap and shorter two-phase coexistence region. Finally, in small MoO2 nanocrystals, the structural evolution during lithiation becomes entirely single-phase/solid-solution. For all nanostructured materials, the changes to the phase transition dynamics lead to dramatic improvements in capacity, rate capability, and cycle life. This work highlights the continuous evolution from a kinetically hindered battery material in bulk form to a fast-charging, pseudocapacitive material through nanoscale size effects. As such, it provides key insight into how phase transitions can be effectively controlled using nanoscale size and emphasizes the importance of these structural dynamics to the fast rate capability observed in nanostructured electrode materials.

A first-principles and CALPHAD-assisted phase-field model for microstructure evolution: Application to Mo-V binary alloy systems

A multiscale computational framework combining the first-principles calculations and the CALPHAD approach with the phase-field method is presented to simulate the microstructure evolution in multicomponent steel alloys. We demonstrate the potential of the framework by predicting the microstructural evolution in elastically periodic arrays of the Mo-V binary sub-system. The framework utilizes the first-principles calculations using special quasi-random structures. Hitherto unavailable thermodynamic and material properties of the alloy are obtained by employing the first-principles calculations and the CALPHAD approach and fed into the phase-field model to predict the microstructure evolution at different temperatures within the miscibility gap region. In addition to the temperature and cooling rates, the model incorporates the role of mechanical fields in decomposition kinetics in the Mo-V binary alloy system. Regimes for temperatures and cooling rates at which spinodal decomposition occurs are identified. Applying external loading leads to directional phase separation in the Mo-V binary system. The elastic inhomogeneity in terms of material properties between the two phases initiates the directional alignment while eigenstrains and applied external loading control the degree of alignment. The framework developed is general and extendable to higher multicomponent sub-systems in steel alloys.

Phase stability behavior of (Ti,Al,Si)N multi-principal nitrides regulated by the Si content: Thermodynamics and first principles calculations

The cubic (B1) (rock salt-type) Ti(1−x)AlxN system is one of the most important protective coatings in industry due to properties such as hardness and thermal stability. Moreover, different alloying elements have been studied to increase its working temperature. Silicon has been demonstrated as an interesting option, since it can improve the oxidation resistance and stabilize the system in the hexagonal (B4 wurtzite-type) phase. Different experimental studies have been developed to understand the role of Si in the conformation of Ti(1−x-y)AlxSiyN pseudo-ternary coatings. However, some results seem to be contradictory. Here, we used ab initio and CALPHAD calculations to understand the Si incorporation effects on the phase stability and the critical Si composition. We found that the maximum mixing enthalpy for B1 falls on the TiN-AlN side of the ternary diagram and continues until almost equimolar composition. The B1-B4 phase transition point shifted significantly from x(AlN) = 0.71 without Si to x(AlN) = 0.21 with x(SiN) = 0.4. The critical composition of x(SIN) = 0.06 was found, where the miscibility gap region increased, demonstrating unfavorable results if going higher in Si content.The ab-initio calculations showed that the inclusion of silicon reduced the mechanical properties of the B1 phase, but at the critical threshold of 10 at% of silicon content, the mechanical properties did not significantly diminished. Calculated diagrams at equilibrium conditions mapped out the phase evolution to determine the phase transition paths and phase dependence on common coating deposition parameters. These results could serve as a reference for the experimental obtaining of improved hard coatings based on the (Ti,Al,Si)N multi-principal nitride.

The thermophysical properties of Bi-Ga alloys

In this work, an experimental study was conducted to show the effect of Ga addition to Bi-Ga alloys on density, surface tension, and viscosity. The thermophysical properties of the Bi-Ga system in the liquid state were determined using the discharge crucible method in the temperature range of 573–823 K. The experimental results were compared with the literature data and showed a good correlation on changes for studied properties with Ga addition. The isothermal section at 573 K of the investigated properties shows very good agreement with literature data, and with data obtained from models. Segregation in the liquid has a huge effect on the changes in studied properties. A very big reduction of surface tension value with the addition of Bi content was observed. Moreover, increasing viscosity is connected with the miscibility gap region in the Bi-Ga system.

Experimental investigation of phase equilibria of the Ir-Pt binary system in subsolidus region

Binary phase diagram Ir-Pt system has a wide miscibility gap whose boundaries are difficult to determine due to low diffusion of refractory metals. The system itself has a number of potential applications primarily in catalysis, where addition of iridium to pure platinum promotes higher activity. Therefore, the information about thermodynamic stability of bimetallic particles is necessary for research in this area.The Ir-Pt system was reinvestigated in subsolidus region by means of X-ray diffraction, SEM and TEM. The true equilibrium state of solid solutions in miscibility gap region was achieved via double-sided approach. Pairs of samples, mixture of pure metals and single-phase solid solution, were annealed at different temperatures until the equal phase composition is reached. To shorten annealing time needed for reaching the state of equilibrium, the porous nanosized samples were used, which were prepared from the mixture {(NH4)2[PtCl6] + (NH4)2[IrCl6]} and solid solution of corresponding complex salts(NH4)2[Ir0.5Pt0.5Cl6]. The temperature range was 600–1400 °C. The boundaries of miscibility gap revealed to be significantly lower than stated before, the critical point position was estimated to be ~ 790 °C at 55 at% Pt. The approach can be suitable for investigation in other refractory metals binary systems.

Investigation of the miscibility gap region in liquid Ga–Pb alloys

Abstract The miscibility gap of the Ga–Pb system has been investigated by different experimental methods and techniques. Viscosity, acoustic and electrical conductivity measurements were carried out through the entire immiscibility region. Possible reasons of revealed discrepancies in the absolute values of the phase separation temperatures are discussed in relation with peculiarities of the experimental methods employed. The shape of the miscibility gap has been analysed.

Preparation of Structural Phase Diagram of Nd2Ni1-X Cu x O4+δ As New Cathode Materials – Clarification of Existence of Miscibility Gap

Nd2NiO4+δ with K2NiF4 type structure (T-phase) composed of rock salt layer and perovskite layer has attracted much interest as new cathode material for solid oxide fuel cell. It was reported that partial substitution of Cu for Ni-site in Nd2NiO4+δ improved ionic and hole conductivity [1]. However, crystal structure must change depending on Cu content, resulting in possible variation of electrical property, since crystal structure of Nd2CuO4 is T’-phase composed of fluorite layer and [CuO2] sheet, which is completely different from T-phase. For optimization of Cu content in Nd2Ni1-x Cu x O4+δ as cathode material, structural phase diagram between Nd2NiO4+δ and Nd2CuO4+δshould be established. In this study, preparation of Nd2Ni1-x Cu x O4+δ with various compositions was attempted and stability at high temperature was evaluated to establish structural phase diagram. It has been established that there exists miscibility gap in Nd2Ni1-x Cu x O4+δ for 0.4≤x≤0.9 for the first time. Nd2Ni1-x Cu x O4+δ (0.0≤x≤1.0) were prepared by the Pechini method by which preparation of homogeneous specimens can be expected. Nd2O3, Ni(NO3)2·6H2O and CuO powders were dissolved with mixture of dilute HNO3 and H2O2, distilled H2O and dilute HNO3, respectively. They were mixed with nominal composition. After mixing ethylene glycol and citric acid, the mixture was heated at about 450 °C, resulting in precursor. The precursor obtained was calcined at 700 °C for 24 h in air, followed by pressing into pellet and heat-treatment at 1000 – 1200 °C in air for 10 h. For identification of the crystal structure and evaluation of the lattice constants, X-ray diffraction measurement (XRD) was performed. Some XRD patterns were analyzed using the Rietveld analysis employing program RIETAN-FP [2]. Homogeneity of the specimens was evaluated by SEM-EDX analysis (JEOL: JCM-5700 equipped with JED-2300). Temperature dependence of lattice constants and molar volume and existence of the structural phase transition were evaluated using high-temperature X-ray diffraction measurements in the air. XRD patterns at room temperature of Nd2Ni1-x Cu x O4+δ prepared at 1200 °C could be indexed as single orthorhombic T-phase with space group of Fmmm (No. 69) and single tetragonal T-phase with I4/mmm (No.131) for 0.0≤x≤0.1 and 0.2≤x≤0.3, respectively. For diffraction patterns of 0.4≤x≤0.9, peaks assigned as T’-phase were observed in addition to ones indexed as T-phase. With increasing Cu content, intensity of the peaks indexed as T’-phase increased and ones assigned as T-phase decreased. All the peaks of XRD pattern for the specimen with x=1.0, i, e., Nd2CuO4+δ was successfully indexed as tetragonal T'-phase with space group of I4/mmm (No.131). Rietveld analysis revealed that lattice constants and molar volume of both T-phase and T’-phase in the specimens with 0.4≤x≤0.9 were independent on Cu content, indicating existence of miscibility gap for 0.4≤x≤0.9. Also revealed by Rietveld analysis was linear relationship between Cu content and molar ratio of T’-phase which could be ascribed to satisfaction of lever rule in the miscibility gap. EDX image and spectra of Nd2Ni0.4Cu0.6O4+δ depicted in Fig. 1 indicate that two phases with Ni rich and Ni poor composition coexist in the specimen, showing agreement with proposed miscibility gap by Rietveld analysis. High temperature XRD measurements revealed that the miscibility gap for 0.4≤x≤0.9 was maintained up to 1000 °C. For the specimens prepared at 1000 °C, the miscibility gap was observed for 0.3≤x≤0.9, suggesting expansion of the miscibility gap region by decreasing temperature.

Preparation of Structural Phase Diagram of Ln2Ni1-X Cu x O4+δ (Ln=La, Pr, Nd, Sm, Eu) as New Cathode Materials: Variation of Structural Phase Diagram on Kinds of Ln

Ln2NiO4+δ (Ln=La, Pr, Nd) with K2NiF4 structure (T-phase) has attracted much interest as new cathode material for solid oxide fuel cells. It was reported that partial substitution of Cu for Ni-site in Pr2NiO4+δ improved ionic and hole conductivity [1]. For development of superior cathode material, Cu content should be optimized. It is expected that crystal structure must change depending on Cu content, resulting in possible variation of electrical property, since crystal structure of Ln2CuO4 (Ln=Pr, Nd) is T’-phase, which is different from T-phase. In the former presentation, structural phase diagram of Nd2Ni1-x Cu x O4+δ with existence of miscibility gap has been reported. Since the crystal structure and electrical property also depend on kinds of Ln, as reported by Miyoshi and coworkers [1], optimization of not only Cu content but also kinds of Ln are also required. In this study, preparation of Ln2Ni1-x Cu x O4+δ (Ln=La, Pr, Nd, Sm, Eu) with various compositions was attempted and stability at high temperature was evaluated to establish structural phase diagram. In particular, variation of miscibility gap region on kinds of Ln was investigated. Ln2Ni1-x Cu x O4+δ (Ln=La, Pr, Nd, Sm, Eu) was prepared by the Pechini method by which preparation of homogenous specimen can be expected. La2O3, Pr6O11, Nd2O3, Sm2O3, Eu2O3 and CuO powder were dissolved with mixture of dilute HNO3 and H2O2. Ni(NO3)2·6H2O powder was dissolved with distilled H2O. They were mixed with nominal composition. After addition of ethylene glycol and citric acid, the mixture was heated at about 450 ºC, resulting in precursor. The obtained precursor was calcined at 700 ºC for 24 h in air, followed by pressing into pellet and heat-treatment at 1000-1200 ºC in air for 10 h. For identification of the crystal structure and evaluation of the lattice constants, X-ray diffraction measurements (XRD) were performed. Some XRD patterns were analyzed using Rietveld analysis employing program RIETAN-FP [2]. Homogeneity of the specimens was evaluated by SEM-EDX analysis (JEOL: JCM-5700 equipped with JED-2300). Temperature dependence of crystal structure and stability at high temperature were evaluated using high-temperature XRD in air. XRD patterns at room temperature of La2Ni1-x Cu x O4+δ prepared at 1200 ºC could be indexed as single tetragonal T-phase and single orthorhombic T-phase for 0.1≤x≤0.8 and 0.9≤x≤1.0, respectively. Pr2Ni1-x Cu x O4+δ with 0.0≤x≤0.4 prepared at 1200 ºC could be identified as single orthorhombic T-phase at room temperature. XRD patterns at room temperature of Nd2Ni1-x Cu x O4+δ prepared at 1200 ºC could be indexed as single orthorhombic T-phase and single tetragonal T-phase for 0.0≤x≤0.1 and 0.2≤x≤0.3, respectively. For diffraction patterns of 0.5≤x≤0.95 in Pr2Ni1-x Cu x O4+δ and 0.4≤x≤0.9 in Nd2Ni1-x Cu x O4+δ , peaks assigned as T’-phase were observed in addition to ones indexed as T-phase. With increasing Cu content, intensity of the signals indexed as T’-phase increased and ones assigned as T-phase decreased. All the peaks of XRD pattern for the specimens with x=1.0, i. e., Pr2CuO4 and Nd2CuO4 were successfully indexed as tetragonal T’-phase. Ln2Ni1-x Cu x O4+δ (Ln=Sm, Eu) for 0.95≤x≤1.0 prepared at 1000 ºC could be indexed as single tetragonal T’-phase. Contrary to Ln2Ni1-xCuxO4+δ with Ln=La, Pr, Nd, T-phase was never observed for the specimens with xless than 0.95. Rietveld analysis revealed that the lattice constants and molar volume of both T-phase and T’-phase in the specimens with 0.5≤x≤0.95 in Pr2Ni1-x Cu x O4+δ and 0.4≤x≤0.9 in Nd2Ni1-x Cu x O4+δ were independent on Cu content, indicating existence of miscibility gap for 0.5≤x≤0.95 in Pr2Ni1-x Cu x O4+δ and 0.4≤x≤0.9 in Nd2Ni1-x Cu x O4+δ . Also revealed by Rietveld analysis was linear relationship between Cu content and molar ratio of T’-phase in the both miscibility gaps, which corresponded to lever rule. EDX image and spectra of Pr2Ni1-x Cu x O4+δ with 0.5≤x≤0.95 and Nd2Ni1-x Cu x O4+δ with 0.4≤x≤0.9 indicated that the specimens were composed of two phases with Ni rich and Ni poor composition and that ratio of Ni and Cu in both phase was almost constant irrespective of x, showing agreement with the proposed miscibility gap by Rietveld analysis. Fig. 1 shows relationship between tolerance factor and Cu content in Ln2Ni1-x Cu x O4+δ . The miscibility gap was roughly observed for tolerance factor between 0.855 and 0.865, suggesting that ionic radius of Ln mainly affected crystal structure of Ln2Ni1-x Cu x O4+δ . High temperature XRD measurements revealed that the miscibility gap for 0.5≤x≤0.95 in Pr2Ni1-x Cu x O4+δ was maintained up to 700 ºC. Above 800 ºC, decomposition was observed. Also revealed from high temperature XRD that the miscibility gap for 0.4≤x≤0.9 in Nd2Ni1-x Cu x O4+δ was maintained up to 1000 ºC.

Preparation of polymeric foams with a pore size gradient via Thermally Induced Phase Separation (TIPS)

Foams with a pore size gradient are promising materials for tissue engineering applications where a complex architecture involving morphological variations in space must be mimicked, e.g. in bone tissue repair. In this paper, a technique to obtain a porous scaffold with a pore size gradient is presented. The preparation procedure is based on Thermally Induced Phase Separation (TIPS), by imposing a different thermal history on the two sides of a polymeric solution. In this way, a gradient in thermal history is produced, which will generate a pore size monotonously varying along scaffold thickness. By controlling some parameters easy to manipulate, such as demixing temperature and/or residence time in the miscibility gap region, the pore size range can be easily tuned.

Thermodynamics of α′(Fe-Rich bcc) + α″(Cr-Rich bcc) → α(bcc) and α para → α ferro Transformations in Fe-20 wt pct Cr Alloy: Drop Calorimetry Study and Elucidation of Magnetic Contribution to Phase Stability

There is considerable uncertainty among diverse assessments of phase equilibrium in Fe-Cr alloys, especially around (α′ + α″)/α miscibility gap region. This is largely due to the difficulty associated with the rigorous incorporation of the interplay between magnetic and chemical contribution to phase stability, in particular its composition and temperature dependencies through theory, in the absence of reliable experimental data. Toward this cause, accurate enthalpy measurements have been made on homogenized Fe-20 wt pct Cr alloy using inverse drop calorimetry, in the temperature range 298 K to 1473 K (25 °C to 1200 °C). The experiments revealed two distinct phase transformations: (i) at 720 ± 10 K (447 ± 10 °C), the Fe-20Cr alloy transformed from α′(Fe-rich) + α″(Cr-rich) two-phase microstructure to α single phase and (ii) at 925 ± 10 K (652 ± 10 °C), the ferromagnetic single-phase α transformed to paramagnetic state. Both these transformations are clearly attested by the measured enthalpy increment variation with temperature. The enthalpy data obtained in this study have been combined with available literature information to forge an integrated theoretical assessment of the energetic aspects of α′ + α″ → α, and α ferro → α para transformations. In addition, a comprehensive evaluation of enthalpy and heat capacity data for Fe-20Cr alloy in the temperature range 0 K to 1473 K (−273 °C to 1200 °C), with explicit incorporation of magnetic contribution has also been made.

Viscosity of liquid binary Pb–Zn alloys in the miscibility gap region

The shear viscosity studies were performed for the liquid Pb–Zn monotectic system over a wide temperature range using an oscillating-cup viscometer, with special attention to the critical point (CP) region. The critical parameters describing the peculiarities of the viscosity behavior in the vicinity of CP are evaluated. The data analysis is based on the dynamic theory of phase transitions and the viscosity equation, which takes into account a spatial dispersion of the systems near their critical temperatures. The results are compared with available data for immiscible dielectric solutions.

Spinodal decomposition and droplets entrapment in monotectic solidification

In this article, we present two models to simulate solidification morphologies in monotectic alloys. With the first model, we investigate the morphological evolution under the influence of spinodal decomposition. The model requires that a gradient energy contribution for the concentration field should be incorporated, in order to stabilize phase separation when the liquid concentration is inside the region of miscibility gap. The free energy of the system in this model is derived from direct interpolation of the bulk energy densities. This, however, results in simulation regions in nanometer scale due to contributions from the chemical free energy of the system to the total surface excess. With the second model, our purpose is to develop a phase-field model to simulate scales that are larger than nanometer, where the departures from equilibrium are very small resulting in phase concentrations outside the spinodal region. In view of this, we exclude the concentration gradient contribution to the grand chemical potential functional, and develop a model based on [M. Plapp, Phys. Rev. E 84, 031601 (2011); A. Choudhury and B. Nestler, Phys. Rev. E 85, 021602 (2012)]. The advantage is that the free energy excess across the interface at equilibrium disappears, and hence it is easier to derive the required surface energies with higher interface widths. Due to this benefit, we employ the method to simulate the dynamic entrapment process in the monotectic reaction and study the influence of liquid(1) - liquid(2) surface energy and undercooling on the entrapment process.

Solid–liquid equilibria, thermochemical and microstructural studies of binary organic monotectic and eutectic alloy

Abstract The phase diagram of 1,4-dibromobenzene (DBB) with pyrogallol (PG) shows the formation of a monotectic and a eutectic alloys at 0.12 and 0.99 mol fractions of DBB, respectively. The phase equilibrium shows the large miscibility gap region with the upper consolute temperature 159.0 °C at 0.55 mol fraction of DBB. Growth kinetics of pure compounds and their monotectic and eutectic at different undercooling (ΔT) obey Hillig–Turnbull's equation: v = u (ΔT)n. Thermodynamic parameters such as enthalpy of mixing, entropy of fusion, interfacial energy, roughness parameters and excess thermodynamic functions were computed based on enthalpy of fusion values obtained from DSC studies. The Cahn wetting condition is applicable for monotectic alloy. The optical microphotographs of binary alloys show lamellar and dendritic features.

Thermodynamic assessment of Au–Pt system

The thermodynamic re-assessment of Au–Pt binary system was carried out by using the Calphad method and based on the recent experimental data. The Gibbs energies of face-centred cubic and liquid phases were described by a sub-regular solution model with the Redlich-Kister equation. Much effort was taken to reproduce the phase equilibrium results and thermodynamic properties of the solid phase, including the activity and mixing enthalpy. The constraint of the third law of thermodynamics was also considered in the assessment. According to the presently assessed results, the miscibility gap region in the Au–Pt system slightly shifts to the Au-rich side, and the critical point of the miscibility gap is about 1200 °C and Au–56% Pt.

Phase Stability and Elasticity of TiAlN.

We review results of recent combined theoretical and experimental studies of Ti1−xAlxN, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient pressure, as well as at pressure of 10 GPa, show a wide miscibility gap and broad region of compositions and temperatures where the spinodal decomposition takes place. The strong dependence of the elastic properties and sound wave anisotropy on the Al-content offers detailed understanding of the spinodal decomposition and age hardening in Ti1−xAlxN alloy films and multilayers. TiAlN/TiN multilayers can further improve the hardness and thermal stability compared to TiAlN since they offer means to influence the kinetics of the favorable spinodal decomposition and suppress the detrimental transformation to w-AlN. Here, we show that a 100 degree improvement in terms of w-AlN suppression can be achieved, which is of importance when the coating is used as a protective coating on metal cutting inserts.

Microstructure and properties of the in situ formed amorphous-crystalline composites in the Fe–Cu-based immiscible alloys

The paper presents microstructures and mechanical properties of the melt-spun Fe 30Cu 32Si 13B 9Al 8Ni 6Y 2 and Fe 44Cu 18Si 13B 9Al 8Ni 6Y 2 alloys. It was found that liquid phase separation of the initially homogeneous melt occurred due to a positive heat of mixing between two major elements. The microstructures of the melt-spun ribbons were composed of the Fe-rich amorphous and the Cu-rich crystalline phases. A significant effect of the melt ejection temperature and the chemical composition (Fe and Cu content) on microstructures of rapidly solidified alloys was revealed. The microstructures of ribbons melt-spun from the miscibility gap region were non-uniform. On the other hand the microstructures of ribbons melt-spun from homogeneous melt temperature region were composed of the spherical precipitates distributed within the matrix. Superior hardness values of the examined ribbons melt-spun from the same temperature were found for the alloy with higher iron content. An increase of the melt-ejection temperature in the homogeneous melt region resulted in hardness decrease in case of the Fe 30Cu 32Si 13B 9Al 8Ni 6Y 2 alloy and its increase for the Fe 44Cu 18Si 13B 9Al 8Ni 6Y 2 ribbons.

Novel organic monotectic alloy and its thermal, physicochemical, and microstructural studies

The phase diagram study of an organic analogue of a nonmetal–nonmetal system involving 4-bromochlorobenzene and resorcinol shows the formation of a eutectic and a monotectic. The phase equilibrium shows the large miscibility gap region with the consolute temperature 143.0 °C. Growth kinetics of the eutectic, the monotectic and the pure components studied at different undercooling, suggests the applicability of Hillig–Turnbull’s equation. For binary materials and parent compounds, the heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were calculated from the enthalpy of fusion values determined by the DSC method. The solid–liquid interfacial energy shows the applicability of Cahn’s wetting condition. The effects of solid–liquid interfacial energy on solidification behaviour of monotectic alloy have also been discussed. The microstructures of monotectic and eutectic show the uniform array of droplets and broken lamella, respectively.

Study of the liquidus and solidus surfaces in the quaternary Fe-Ni-Cu-S system: III. Construction of a meltability diagram and determination of miscibility gap boundaries for the ternary Cu-Ni-S sulfide system

This work is a continuation of the cycle of studies dealing with the phase transformations occurring in the ternary systems bounding the quaternary Fe-Ni-Cu-S system. A meltability diagram is plotted for the ternary Cu-Ni-S sulfide system using differential thermal analysis, scanning electron microscopy, and electron-probe microanalysis, and miscibility gap boundaries and the positions of conodes in the miscibility gap region of this system are determined. A solidus surface is plotted for the Cu-Ni-S system for the first time.

Viscosity of liquid In–Se–Tl alloys in the miscibility gap region

The shear viscosity measurements were performed for liquid In x Se 20Tl 80− x (0 ≤ x ≤ 80 at.%) alloys over a wide temperature range above the monotectic using an oscillating-cup viscometer. In this range the ternary In–Se–Tl system may be considered as a set of “quasibinary” immiscible metal-chalcogen alloys of critical composition. Variation of the In/Tl ratio at a constant Se content changes the properties of the coexisting liquids and affects the temperature of demixing. The critical parameters describing the peculiarities of the viscosity behavior in the vicinity of the critical point are evaluated. Based on the dynamic theory of phase transitions a description of the viscosity in the region of phase separation is proposed. The results are compared with available data for immiscible dielectric solutions and metallic melts.

Viscosity of liquid Ga-Pb alloys in the miscibility gap region

Viscosity of liquid Ga-Pb alloys in the miscibility gap region