Pseudo-binary Phase Diagram Research Articles

Sn-Se Binary and Cu-Sn-Se Ternary Thin Films Grown by Co-Evaporation Process

Unfavorable secondary phases like binaries and ternaries are often observed in synthesizing Cu2ZnSnSe4 (CZTSe) quaternary crystal due to its narrow phase space, which strongly limits the performance of Kesterite solar cells. To identify the growth parameters against the stability of these secondary phases, we systematically studied the growth process of Sn-Se binaries and Cu-Sn-Se ternaries using co-evaporation method. We found that the compositions of Sn-related binary and ternary phases were strongly dependent on the substrate temperature and Se flux during deposition, which will be helpful in designing formation paths for quaternary system. Growth temperature of CZTSe higher than 490 °C will make the thin film free of Cu2SnSe3 phase. Our experiments also suggest that formation pathways in the Cu2SnSe3-ZnSe pseudobinary phase diagram at a slightly lower substrate temperature deserve more experimental and theoretical considerations because of its easier composition control.

Calculation of Solidification‐Related Thermophysical Properties of Steels Based on Fe‐C Pseudobinary Phase Diagram

In order to be accurate for the reliability of real‐time heat transfer model for online control of continuous casting process of steel and also to be easily embeddable, special algorithms have been developed for calculation of solidification‐related thermophysical properties of carbon and low alloy steels. These thermophysical properties include density, thermal conductivity, and enthalpy‐related data, i.e., enthalpy and specific heat. In the algorithms, Fe‐C pseudobinary phase diagram, which is similar to Fe‐C phase diagram but is influenced by contents of steel alloying elements other than carbon, has been introduced as the basis to solve the phase fractions of steel as functions of temperature. Associated with the solved phase fractions, the thermophysical properties can be calculated from 1600 to 0 °C by combining corresponding data of different phases, which are fitted as polynomial functions of temperature and steel composition. Finally, the algorithms have been tested as the calculated results showed good agreement with the calculated data by software JMatPro and also the measured data.

Phase behavior of Safaniya vacuum residue

The phase behavior of Safaniya vacuum residue (Saudi Arabia) from (200 to 520) K at atmospheric pressure was investigated and the phase states were determined from nanofiltered samples with pentane-asphaltene mass fractions wA between 0.048 and 0.555 based on joint treatment of heat capacity data from differential scanning calorimetry and phase angle data from rheological measurements. SARA and elemental composition data of the oil are also considered and some assumptions on more detailed oil chemistry have been made based on a predictive heat capacity correlation. A pseudo binary phase diagram is constructed based on the behavior of retentate free permeate and permeate free retentate. Compositionally, these materials comprise pentane maltenes and asphaltenes respectively to a first approximation. These pseudo-components, partitioned at 473K, are shown to behave independently. A broad phase transition arising in Safaniya vacuum residue phase behavior is shown to comprise overlapping but independent transitions in these two pseudo components. The temperature range of the combined glass+melting transition depends on sample thermal history (both long-term and short-term). Based on this representation, Safaniya vacuum residue comprises four phases drawn from crystalline and liquid maltene-rich phases as well as crystalline and liquid asphaltene-rich phases from 265K to 360–370K. It is also shown that the phase behavior of chemically separated pentane asphaltenes differs significantly from that of the nanofiltered asphaltene-rich material. The phase diagram of Safaniya vacuum residue is compared with that of Maya crude oil [M. Fulem, et al. Fluid Phase Equilib. 272 (2008) 32–41] and Athabasca bitumen [A. Bazyleva, et al. J. Chem. Eng. Data 56 (2011) 3242–3253]. The differences in the phase behavior of these oils are traced to differences in their composition.

Combined force spectroscopy, AFM and calorimetric studies to reveal the nanostructural organization of biomimetic membranes

In this work we studied a binary lipid matrix of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (POPG), a composition that mimics the inner membrane of Escherichia coli. More specifically, liposomes with varying fractions of POPG were analysed by differential scanning calorimetry (DSC) and a binary phase diagram of the system was created. Additionally, we performed atomic force microscopy (AFM) imaging of supported lipid bilayers (SLBs) of similar compositions at different temperatures, in order to create a pseudo-binary phase diagram specific to this membrane model. AFM study of SLBs is of particular interest, as it is conceived as the most adequate technique not only for studying lipid bilayer systems but also for imaging and even nanomanipulating inserted membrane proteins. The construction of the above-mentioned phase diagram enabled us to grasp better the thermodynamics of the thermal lipid transition from a gel-like POPE:POPG phase system to a more fluid phase system. Finally, AFM force spectroscopy (FS) was used to determine the nanomechanics of these two lipid phases at 27°C and at different POPG fractions. The resulting data correlated with the specific composition of each phase was calculated from the AFM phase diagram obtained. All the experiments were done in the presence of 10mM of Ca2+, as this ion is commonly used when performing AFM with negatively charged phospholipids.

Effect of Welding Current and Time on the Microstructure, Mechanical Characterizations, and Fracture Studies of Resistance Spot Welding Joints of AISI 316L Austenitic Stainless Steel

This article aims at investigating the effect of welding parameters, namely, welding current and welding time, on resistance spot welding (RSW) of the AISI 316L austenitic stainless steel sheets. The influence of welding current and welding time on the weld properties including the weld nugget diameter or fusion zone, tensile-shear load-bearing capacity of welded materials, failure modes, energy absorption, and microstructure of welded nuggets was precisely considered. Microstructural studies and mechanical properties showed that the region between interfacial to pullout mode transition and expulsion limit is defined as the optimum welding condition. Electron microscopic studies indicated different types of delta ferrite in welded nuggets including skeletal, acicular, and lathy delta ferrite morphologies as a result of nonequilibrium phases, which can be attributed to a fast cooling rate in the RSW process. These morphologies were explained based on Shaeffler, WRC-1992, and pseudo-binary phase diagrams. The optimum microstructure and mechanical properties were achieved with 8-kA welding current and 4-cycle welding time in which maximum tensile-shear load-bearing capacity or peak load of the welded materials was obtained at 8070 N, and the failure mode took place as button pullout with tearing from the base metal. Finally, fracture surface studies indicated that elongated dimples appeared on the surface as a result of ductile fracture in the sample welded in the optimum welding condition.

Production of Zr-Based Metallic Glass Matrix Composites by Semisolid Process

It was reported that micrometer-sized ductile crystalline phases can improve the ductility of Zr-based bulk metallic glasses. The present authors reported the synthesis of bulk metallic glass composites by a process combining cooling slope casting and suction casting for Zr66.4Nb6.4Cu10.5Ni8.7Al8 alloys. This study aims to investigate basics of Zr-based metallic glass matrix composites with semisolid structure. As a result, it was found that the Zr-based metallic glass matrix composites with very uniform semisolid structure can be produced by heat treatment process at semisolid region. Moreover, it was found that experimental results can be explained by the pseudo-binary phase diagram.

Resistance spot welding joints of AISI 316L austenitic stainless steel sheets: Phase transformations, mechanical properties and microstructure characterizations

In this paper, we aim to optimize welding parameters namely welding current and time in resistance spot welding (RSW) of the austenitic stainless steel sheets grade AISI 316L. Afterward, effect of optimum welding parameters on the resistance spot welding properties and microstructure of AISI 316L austenitic stainless steel sheets has been investigated. Effect of welding current at constant welding time was considered on the weld properties such as weld nugget size, tensile–shear load bearing capacity of welded materials, failure modes, failure energy, ductility, and microstructure of weld nuggets as well. Phase transformations that took place during weld thermal cycle were analyzed in more details including metallographic studies of welding of the austenitic stainless steels. Metallographic images, mechanical properties, electron microscopy photographs and micro-hardness measurements showed that the region between interfacial to pullout mode transition and expulsion limit is defined as the optimum welding condition. Backscattered electron scanning microscopic images (BE-SEM) showed various types of delta ferrite in weld nuggets. Three delta ferrite morphologies consist of skeletal, acicular and lathy delta ferrite morphologies formed in resistance spot welded regions as a result of non-equilibrium phases which can be attributed to the fast cooling rate in RSW process and consequently, prediction and explanation of the obtained morphologies based on Schaeffler, WRC-1992 and Pseudo-binary phase diagrams would be a difficult task.

Crystallization of belite–melilite clinker minerals in the presence of liquid phase

Crystallization of belite–melilite clinker minerals was studied from the view point of a high temperature equilibrium. Ca2SiO4–Ca2Al2SiO7 and Ca2SiO4–Ca2AlFeSiO7 clinkers were synthesized at 1330°C–1650°C. The constituent phases were determined by X-ray powder diffractometry and optical microscopy. Chemical compositions of the individual clinker minerals were determined using an electron probe microanalyzer.We established the two types of P2O5-bearing pseudobinary phase diagrams in the systems Ca2SiO4–Ca2Al2SiO7 at 1505°C–1650°C and Ca2SiO4–Ca2(Al,Fe)2SiO7 at 1330°C–1550°C. In the latter system, the liquid phase appeared at 1390°C, which is approximately 150°C lower than the temperature of liquid formation in the former system. The melilite phenocrysts larger than 50μm were observed not only in the slowly cooled Ca2SiO4–Ca2(Al,Fe)2SiO7 clinker but also in commercial belite–melilite clinkers. These crystals would be nucleated and grown from a liquid phase which was formed at relatively low temperatures.

Computational Thermodynamic Modeling of Mixed Polyanion Glasses for Lithium Ion Battery Cathode Materials

We have used computational thermodynamic approach to model Lithium-bearing mixed polyanion (LBMP) as an effort to predict electrochemical properties of glass cathode materials. Individual LBMP have been modeled within the framework of the compound energy formalism (CEF) as implemented in the CALPHAD (CALculation of PHAse Diagram) approach [1, 2].To model the baseline material Li/FePO4 thermodynamic descriptions for the crystalline solid and liquid phases of constituent Fe2O3 and P2O5 have been taken from the Scientific Group Thermodata Europe (SGTE) Substance Database and used as reference states. Thermodynamic model parameters for FePO4 and Fe4(P2O7)3 have been self-consistently evaluated to reproduce Fe2O3-P2O5 pseudo-binary phase diagram reported in the literatures. Afterward thermodynamic model parameters for the FePO4-LiFePO4 pseudo-binary system has been evaluated to represent experimentally determined phase equilibrium data [3, 4]. The model successfully reproduces the miscibility gap at low temperatures by introducing positive interaction between FePO4 and LiFePO4.FIG. 1. Calculated cell circuit voltage of Li x FePO4 of crystalline and glass phases. Different ratios between the liquid and solid phases of LiFePO4 and FePO4(L:S) have been used to model glass phase.From the developed thermodynamic database the open circuit voltage (OCV) of crystalline and glass Li/FePO4 have been predicted by calculating chemical potential of Li (see FIG. 1). In order to model the Li x FePO4 glass phase, different ratios between the liquid and solid phases of LiFePO4 and FePO4(L:S) have been used and ideal mixing between two end-members have been assumed. The glassy form is more sloping, and has a significantly lower potential.Thermodynamic modeling of Li-Fe2O3-V2O5 has been carried out to incorporate additional polyanion species in the model for the glass cathode materials. From the completed thermodynamic modeling of Li/FeVO4 which combined with the baseline system, the cell voltage of Li/Fe4(0.5P2O7×0.5V2O7)4 has been benchmarked against experimental measurements. The ratio between the solid and liquid thermodynamic descriptions to describe the electrochemical behavior of the LBMP glass materials has been established and will be used for other polyanion species to be added in the baseline system. Acknowledgement This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy References [1] L. Kaufman, H. Bernstein, Computer Calculation of Phase Diagram, New York, Academic Press Inc., 1970.[2] N. Saunders, A. P. Miodownik, CALPHAD (Calculation of Phase Diagrams): A Comprehensive Guide, Oxford, New York, Pergamon, 1998.[3] J. L. Dodd, R. Yazami, B. Fultz, Electrochem. Solid State Lett., 9(3): A151-A5, 2006.[4] C. Delacourt, P. Poizot, J. M. Tarascon, C. Masquelier, Nature Mater., 4(3): 254-60, 2005.

Alloy Design of New Ni-Based Structural Materials for Electrolytic Reduction and its Corrosion Behavior in Lithium Molten Salt

In this study, the corrosion behavior of new Ni-based structural materials was studied for electrolytic reduction after exposure to LiCl-Li2O molten salt at 650°C for 24-216h under an oxidizing atmosphere. The new alloys with Ni, Cr, Al, Si, and Nb as the major components were melted at 1700°C under inert atmosphere. The corrosion products and fine structures of the corroded specimens were characterized by SEM, EDS, and XRD. The corrosion rate of 12wt% Cr-2wt% Si alloys and 12wt% Cr-5wt% Si alloys are below 0.3mm/year. However, the corrosion rate of 20wt% Cr-5wt% Si is 0.6mm/year. Also, the corrosion products of 12wt% Cr alloys were Cr2O3, NiCr2O4, Ni, and NiO; those of 20wt% Cr alloys were Cr2O3, LiAl2Cr3O8, and NiO. The higher corrosion rate of 20wt% Cr-5wt% Si could be the higher solute concentration which leads to an unstable alloy formation. As confirmed by the pseudo binary phase diagram of (Ni-Cr-Al-Nb)-Si, the solubility of the silicon with 20 wt% of Cr decreased to 4 wt% from 5 wt% with 12 wt% of Cr.

Phase formation of Cu50−xCoxZr50 (x=0–20at.%) alloys: Influence of cooling rate

The dependence of phase formation on quenching rate and the thermodynamical stability of Cu50−xCoxZr50 (x = 0–20) was investigated. It was found that cobalt decreases the glass forming ability of the alloys and changes the crystalline products of the system from Cu10Zr7 + CuZr2 to a (Cu,Co)Zr phase with a B2 structure. The results indicate that for the melt-spun ribbons with at least 5 at.% Co, the glass crystallizes directly into B2 (Cu,Co)Zr, while in the case of bulk specimens, compositions with 0 ⩽ x < 5 of Co contain the monoclinic (Cu,Co)Zr phase as well as Cu10Zr7 and CuZr2, whereas for x ⩾ 10, the B2 (Cu,Co)Zr phase is the equilibrium phase at room temperature. Complete solubility of cobalt in B2 CuZr is indicated by the linear change of the lattice constant, which can be readily understood by Vegard’s law. Furthermore, increasing the cobalt content decreases the martensitic transformation temperatures. The phase formation in the ternary system is summarized in a pseudo-binary (Cu,Co)Zr phase diagram. The results are useful for designing new shape memory alloys, as well as bulk metallic glass composites with the addition of glass former elements.

Copper-Magnesium-Manganese Spinel Coatings for Solid Oxide Fuel Cell Interconnects

The properties of Cu-Mn-O spinels containing Mg were studied for use as protective coatings on UNS430 stainless steel interconnects in solid oxide fuel cells. Cu-Mn-Mg-O spinel coatings were formed by oxidizing electrodeposited copper, manganese, and magnesium hydroxide films in air at 800°C. A base layer of copper aided uniform manganese deposition and uniform spinel formation. The Mg-Mn-O pseudobinary phase diagram based on XRD results shows a wide range of spinel non-stoichiometry. The CuMn2O4 spinel coating has higher conductivity (∼100 S/cm at 800°C) but exhibited buckling defects. Addition of magnesium to the Cu-Mn-O spinel coatings significantly reduced the buckling damage. Although the measured electrical conductivity of MgMn2O4 is 1–2 S/cm at 800°C, Cu0.7Mg0.3Mn2O4 has a conductivity of ∼60 S/cm at 800°C. Cu-Mn-Mg-O spinel coatings also protect stainless steel by significantly reducing chromium oxide scale formation and diffusion of chromium into the coatings with the advantage of relatively high conductivity.

Local Changes of Microhardness in Dissimilar Weld Joints after High Temperature Exposure

The paper presents results obtained during evaluation of dissimilar weld joints of creep-resistant steels. During high temperature exposure of dissimilar weld joints, alloying elements were redistributed across the weld interface. These diffusion effects can cause local changes of microstructure and have a direct effect on local mechanical properties in weld interface area. Carbon and nitrogen have the strongest influence on changes of mechanical properties of steels. . These local changes of mechanical properties have a strong influence on the reliability and the service live of the whole welded structures. The dissimilar joints of the austenitic steel/martenzitic steel type was studied. Laboratory weld joints were prepared and annealed at different temperatures for different time periods. Microhardness profiles across the weld interface were measured and the influence of long-term, high temperature exposure on the changes of local microhardness was evaluated. Results were compared with pseudo-binary phase diagrams and with the literature.

A Pseudo-Binary Diagram of the (Bi,Pb)-Sr-Ca-Cu-O System

A pseudo-binary phase diagram of the (Bi,Pb)-Sr-Ca-Cu-O system along the Bi1.6Pb0.4Sr2Can-1CunOx line is constructed. This resulting phase diagram shows three kinds of peritectic reactions, one eutectic reaction and one peritectoid reaction. The equilibrium solid phases in this diagram are the 2201 (n=1), 2212 (n=2), 2223 (n=3) and (Sr,Ca)CuO2 (n→∝) phases. The 2201 phase is solid solution which is stable at 1≤n≤1.2. The eutectic composition point is close to the maximum solid solution composition of the 2201 phase. The temperature interval between the peritectic reaction of L + (Sr,Ca)2CuO3 + (Sr,Ca)CuO2 → 2212 and the eutectic reaction of L → 2201 + 2212 is only about 3°C. For the composition of n=3, CaO and the liquid phase are stable at temperatures above 940°C. During the cooling, these two phases react peritectically to (Sr,Ca)2CuO3. At around 890°C, (Sr,Ca)2CuO3 reacts with the liquid to produce (Sr,Ca)CuO2. At around 865°C, (Sr,Ca)2CuO3 and (Sr,Ca)CuO2 react with the liquid to produce the 2212. The 2223 phase is transformed by a peritectoid reaction of the 2212 phase and residual (Sr,Ca)2CuO3, (Sr,Ca)CuO2.

The effect of structural vacancies on the thermoelectric properties of (Cu2Te)1−x(Ga2Te3)x

Abstract We have studied the effects of structural vacancies on the thermoelectric properties of the ternary compounds (Cu 2 Te) 1− x (Ga 2 Te 3 ) x ( x =0.5, 0.55, 0.571, 0.6, 0.625, 0.667 and 0.75), which are solid solutions found in the pseudo-binary phase diagram for Cu 2 Te and Ga 2 Te 3 , and possesses tunable structural vacancy concentrations. This materials system is not suitable due to the cost and scarcity of the constituent elements, but the vacancy behavior is well understood and will provide a valuable test case for other systems more suitable from the standpoint of cost and abundance of raw materials, which also possesses these vacancy features, but whose structural characterization is lacking at this stage. We find that the nominally defect free phase CuGaTe 2 possess the highest ZT ( ZT = S 2 T / ρκ , where S is the Seebeck coefficient and ρ is the electrical resistivity κ is the thermal conductivity and T is the absolute temperature) which approaches 1 at 840 K and seems to continuously increase above this temperature. This result is due to the unexpectedly low thermal conductivity found for this material at high temperature. The low thermal conductivity was caused by strong Umklapp (thermally resistive scattering processes involving three phonons) phonon scattering. We find that due to the coincidentally strong scattering of carriers by the structural defects that higher concentrations of these features lead to poor electrical transport properties and decreased ZT .

Phase Equilibria Studies of Cu-O-Si Systems in Equilibrium with Air and Metallic Copper and Cu-Me-O-Si Systems (Me = Ca, Mg, Al, and Fe) in Equilibrium with Metallic Copper

The pseudo-binary phase diagrams in the Cu-O-Si system in equilibrium with air and metallic copper have been constructed. Equilibration at high temperature in an appropriate containment material, followed by rapid quenching and measurement of phase compositions using an electron probe x-ray microanalysis (EPMA) technique, was carried out to obtain the phase equilibria data. The investigation has been extended to characterize the effects of CaO, MgO, AlO, and ‘‘FeO’’ on the liquidus isotherms of tridymite in equilibrium with metallic copper at temperatures of 1473 K and 1573 K (1200 °C and 1300 °C).

Effect of 2-(4-fluorophenylamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole on the molecular organisation and structural properties of the DPPC lipid multibilayers

Interactions and complex formation between lipids and biologically active compounds are crucial for better understanding of molecular mechanisms occurring in living cells. In this paper a molecular organisation and complex formation of 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole (FABT) in DPPC multibilayers are reported. The simplified pseudo binary phase diagram of this system was created based on the X-ray diffraction study and fourier transform infrared spectroscopic data. The detailed analysis of the refraction effect indicates a much higher concentration of FABT in the polar zones during phase transition. Both the lipid and the complex ripple after cooling. It was found that FABT occupied not only the hydrophilic zones of the lipid membranes but also partly occupied the central part of the non polar zone. The infrared spectroscopy study reveals that FABT strongly interact with hydrophilic (especially PO2−) and hydrophobic (especially “kink” vibrations of CH2 group). The interactions of FABT molecules with these groups are responsible for changes of lipid multibilayers observed in X-ray diffraction study.

Study of α ↔ β transformation in the dimorphic clathrate Ba8Ga16Sn30

The intermetallic clathrate Ba8Ga16Sn30 (BGS) is dimorphic, possessing α-phase (type-VIII) and β-phase (type-I). To determine the stability ranges of the two phases, we performed a study of the phase diagram by combining differential thermal analysis (DTA) and power X-ray diffraction (XRD) on both samples of bulk single crystals (≅1 mm) and powdered crystals (<50 µm). It was found that bulk samples of both α- and β-phases melt congruently at 500°C, but a powder specimen of β-phase has a broad endothermic DTA peak at 466°C, just below the melting point. Intensive studies on this event revealed a partially reversible and strongly kinetically controlled β → α structural phase transition. This transition has been confirmed by in situ synchrotron XRD at SPring-8. After heating the powder specimens to 530°C and cooling to room temperature, the main phase remained intact in both modifications. When the soaking temperature was increased from 530 to 910°C, a weak exothermic peak for nucleation of Ba(Ga/Sn)4 appeared at about 570°C in the cooling process. The main phase of the resulting materials was found to be β-phase, irrespective of the starting phases and grain sizes. Based on the results of DTA and XRD, we constructed a tentative Sn–Ba(Ga/Sn)4 pseudo-binary phase diagram. It suggests that large single crystals of β-BGS can be grown from the Sn flux without being disturbed by the α ↔ β structural phase transition.

Growth of Cu2ZnSnSe4 single crystals from Sn solutions

We investigated the pseudobinary phase diagram of the Cu2ZnSnSe4 (CZTSe)–Sn system in order to obtain the knowledge useful for the growth of high-quality CZTSe single crystals using a solution-based method. For Sn solutions saturated with less than ∼60mol% CZTSe, the solutes are separated into two phases, whereas for Sn solutions with more than 60mol% CZTSe, the solutes are of single phase. The CZTSe single crystals were obtained from a 80mol% CZTSe solution (liquid temperature 850°C) at 900°C. The powder X-ray diffraction pattern of the CZTSe single crystal shows preferred orientations of (112), (220) and (312) planes, confirming the Kesterite structure of CZTSe. The Raman spectrum shows three peaks at 170, 193 and 231cm−1, which correspond to CZTSe peaks. The composition of the CZTSe single crystal along the growth direction is found to be slightly Cu-poor, Zn-rich and Se-rich. Therefore, we obtained good-quality homogeneous CZTSe single crystal grown by Sn solutions.

Construction of a pseudo-binary phase diagram for multi-component Ni-base superalloys

A novel method for the representation of multi-component thermodynamics through a pseudo-binary system without any major assumption is presented. Pseudobinary phase diagrams have been constructed for three representative Ni-base superalloys. Expressions for the Gibbs energy of the different phases as a function of the pseudo-binary composition and temperature have been derived. The information derived from the pseudo-binary phase diagrams and Gibbs energy of the various phases represented through pseudo-binary compositions is applied to (a) solidification calculations for determination of dendrite arm spacing using cellular automata model and (b) phase field calculations.