Calphad-computer Coupling of Phase Diagrams and Thermochemistry最新文献

Sodium-ion batteries have emerged as a promising alternative to lithium-ion batteries due to their lower cost and similar electrochemical properties. The development of high-capacity and long-life electrode materials is crucial for advancing sodium-ion battery research. A significant amount of research has been conducted on the electrochemical properties of NaV₆O₁₅, however, there remains a dearth of data on its thermodynamic properties. Herein, NaV₆O₁₅ was synthesized using the solid-phase sintering method and thoroughly characterized. Thermodynamic data in the temperature ranges of 298.15–900 K, 15–303 K, and 573–873 K were determined using the Neumann-Kopp rule, low-temperature physical property measurement system, and MHTC 96 line, respectively. The heat capacity equation of NaV₆O₁₅ was derived and its enthalpy, entropy, and Gibbs free energy (298.15–800 K) were calculated. Moreover, the thermodynamics of NaV₆O₁₅-related formation and decomposition reactions were analyzed. The obtained heat capacity equation of NaV₆O₁₅ was $C_p=517.05524+0.08612T-1.25053\times 10^7{T}^{-2}\left(J/mol·K\right)\left(298.15\sim 873K\right)$. This study addresses the thermodynamic knowledge gaps of NaV₆O₁₅ and provides valuable insights for its preparation and decomposition in manufacturing processes.

The phase equilibria of the La–Fe–Si system were investigated using a combination of experimental and thermodynamic modeling methods. The isothermal cross-section of the La–Fe–Si ternary system in the (Fe, Si)-rich region at 1373 K was experimentally investigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Based on the experimental results and literature reports of the La–Fe–Si system, the thermodynamic model parameters of the system were optimized using the CALPHAD method. The intermediate compounds in the La–Si binary system and ternary compounds in the La–Fe–Si ternary system were described via sublattice models. The calculated thermodynamic and phase equilibria data were in good agreement with the experimental data, providing a foundation for the development of a multi-component thermodynamic database for LaFeSi-based alloys.

In this study, the solubilities of oxygen in molten La, Gd, Tb, Ho, and Er metals were measured and the oxide phases in equilibrium with each of these lanthanoid metals were identified to systematically determine the liquidus of lanthanoid-oxygen systems in the metal-rich region. The molten lanthanoid metal and lanthanoid oxide pellets were equilibrated at 1573–1873 K and then quenched. The oxygen concentration in the quenched metals was measured using inert gas fusion infrared absorption spectroscopy to determine the oxygen solubilities of molten lanthanoid metals. The crystal structures of the quenched lanthanoid oxide pellets were analyzed using XRD to identify the equilibrium oxide phases, which were identified as the sesquioxides of each lanthanoid element. Furthermore, the Gibbs free energies of the liquid phases of the Ln-O (Ln = La, Pr, Gd, Tb, Dy, Ho, Er) systems were evaluated using the CALPHAD method and thermodynamic software Pandat based on the oxygen solubilities of molten La, Gd, Tb, Ho, and Er metals measured in this study and those of Pr and Dy reported in previous studies.

The phase equilibria of the Co–Zn–Zr ternary system were systematically studied by combining experimental analysis and thermodynamic modelling. The 450 °C isothermal section at the Zn-rich corner and the 600 °C isothermal section of Co–Zn–Zr system were studied by means of scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Seventeen and ten three-phase regions were obtained at 600 and 450 °C isothermal sections, respectively. Three stable ternary compounds named τ₁ (ZrCo₂Zn₂₀), τ₂ (Zr₅Co₃Zn₁₂) and τ₃ (Zr₁₀Co₃Zn₇) were found in the 600 °C isothermal section. Among them, the Bravais lattice symmetry of the τ₂ phase is a simple tetragonal lattice, and its lattice parameters are a = 8.945 Å, b = 8.945 Å, c = 11.737 Å and α = β = γ = 90°. Based on the comprehensive evaluation of the current experimental results and the data reported in the literature, the thermodynamic description of the system was developed using the CALPHAD technique. A set of self-consistent thermodynamic parameters for the Co–Zn–Zr ternary system was obtained with good agreement between the experimental and calculated results.

The development of multi-principal element alloys requires the navigation within a multi-dimensional composition space, which has proven to be challenging. Various methods to predict the state of an alloy, in particular if it is single-phase or not, have been tested with various success. The only approach that can consistently predict the constitution of an alloy, e.g. single-phase, multi-phase, intermetallics, is thermodynamic calculations using Calphad databases. Conventional Calphad databases, such as steel or Ni-base, are of limited use since they are developed for alloys with a specific base element. More suitable databases, such as TCHEA, have been developed, but their development is challenging since they require the inclusion of more subsystems than conventional databases. The predictive capability depends strongly on which elements are considered, and their development is still ongoing. A Calphad database including the elements Al, Co, Cr, Fe, Mn, Ni and C was built up from scratch using mostly assessments of binary and ternary systems from the literature, but with many amendments. This database covers a substantial fraction of the alloys investigated until now plus the element C that is usually not included, but can provide additional strengthening, either in solution or in the form of carbides.

Effects of TiO₂, binary basicity and MgO content on the liquidus temperatures of TiO₂–CaO–SiO₂–MgO–Al₂O₃ slags were experimentally studied in equilibrium with carbon. The experimental techniques include high temperature equilibration, quenching and Electron Probe X-ray Microanalysis (EPMA). It was found that the major primary phase in the composition range investigated is M₃O₅ (M = Ti, Mg, Al). The liquidus temperatures increase with increasing TiO₂ and MgO contents, whereas decrease with increasing CaO/SiO₂ mass ratio. The experimentally determined liquidus temperatures are much higher than the predicted ones by FactSage and the primary phases between the experiment results and predictions are also different. The mole fractions of Al₂TiO₅ and Ti₃O₅ in the M₃O₅ phase decrease, but MgTi₂O₅ increases with increasing MgO content and CaO/SiO₂ in the samples. Moreover, the proportions of Al₂TiO₅ and MgTi₂O₅ in the M₃O₅ phase decrease, while Ti₃O₅ proportion in the M₃O₅ phase increases with increasing the reaction time. The mole ratio of Ti³⁺/Ti⁴⁺ in the M₃O₅ phase decreases with MgO content and CaO/SiO₂ mass ratio in the samples but increases with increasing reaction time.

In this paper, the Sorbitol-Xylitol and Sorbitol-Erythritol two binary systems were computationally investigated. Experimental data including both phase diagrams and thermodynamic information are used as data supports in CALPHAD approach. Four binary phases that in the studied systems: (Erythritol), (Xylitol), (Sorbitol) and liquid are treated as substitution solution. The standard thermodynamic functions of Sorbitol were calculated from the available heat capacity data. Our calculations are in good agreement with the phase diagram data and experimental thermodynamic data available in the literature.

In this paper, 10 groups of ternary Ag–Sn–Zn diffusion couples were prepared under 873, 973 and 1073 K within the fcc single-phase region. The element distribution across the diffusional interface was measured by EPMA, and a high-throughput determination of atomic mobilities in Ag-rich fcc Ag–Sn–Zn alloys was performed by using HitDIC (High-Throughput Determination of Interdiffusion Coefficients, https://hitdic.com/) software in the framework of the numerical inverse method. A self-consistent set of atomic mobility parameters was obtained. Reliability of the evaluated atomic mobility parameters were further verified by reasonably reproducing the experimental composition profiles. Insight into the composition- and temperature-dependence of various diffusion properties in fcc Ag–Sn–Zn alloy were subsequently retrieved and discussed. Furthermore, through the related Arrhenius information, the diffusion frequency factors and diffusion activity energies within the corresponding temperature and the composition range were obtained.

In pursuit of a comprehensive exploration into the diffusion kinetics of bcc Ti–V–Mo alloys, sixteen sets of diffusion couples were prepared within the bcc phase of Ti–V–Mo alloys. These diffusion couples were subjected to annealing at 1373 K and 1473 K. Composition profiles were obtained by means of the electron probe micro-analysis technique (EPMA). The calculation of diffusivities in bcc Ti–V–Mo alloys was performed using the Whittle-Green and Hall methods. Based on available thermodynamic descriptions, the atomic mobility parameters of the bcc Ti–V–Mo system were assessed by using the DICTRA module of the Thermo-Calc software. A comparison is made between the simulated composition-distance curve and the diffusion path with the experimental values, revealing a significant level of concordance.

The diffusion behavior and mechanical properties of the Zr-Nb-Hf system were analyzed using diffusion couple technology and nanoindentation techniques. The diffusion couples were annealed at 1523 K for 24 h, and the compositional profile of the diffusion region was determined using electron probe microanalysis. The main diffusion coefficients, cross-diffusion coefficients, and impurity diffusion coefficients were calculated using the Whittle and Green method, as well as the generalized Hall method. Furthermore, the hardness and Young's modulus of the alloy with different compositions were calculated by Oliver method, based on load-displacement curves obtained from nanoindentation tests. Additionally, the wear resistance and resistance to plastic deformation of the Zr-Nb-Hf alloys were inferred. These results contribute to the existing database of diffusion kinetics and mechanical properties in the Zr-Nb-Hf system, providing valuable references for the development of Zr-Nb-Hf-based alloys with exceptional properties.