CALCULATION OF THERMODYNAMIC PROPERTIES AND PHASE DIAGRAM OF TERNARY MOLTEN SALT SYSTEM NaCl-CaCl_2-SrCl_2 BY USE OF COMPUTOR

本文利用 CaCl-SrCl_2相图中,固相有一个溶解间断区(miscibility gap)的信息,用亚正规溶液模型计算了该二元系液相和固相的 Gibbs 自由能.运用 Toop方程的变通式即最近 Hillert.M.提出的新的非对称方法,由组成 NaCl-CaCl_2-SrCl_2三元系的二元系热力学性质预示了该三元系液相的 Gibbs 自由能,进而用计算机计算了三元液相中各组元的偏克分子 Gibbs 自由能和活度系数.由三元液相中组元 NaCl,CaCl_2和 SrCl_2的过剩偏克分子 Gibbs 自由能,根据相平衡原理,用计算机计算了该三元系的相图.计算结果对于钠电解的实践和盐湖资源的综合利用有实际意义.亚正规溶液模型和新的非对称方法可望适合于计算一系列有潜在重要性的电荷不对称熔盐体系的相图.如对 Na,Ti,Mg,Ce 电解及熔融氯化脱水制取无水氯化镁有实际意义的 NaCl-CaCl_2-BaCl_2,NaCl-SrCl_2-BaCl_2,NaCl-CaCl_2-MgCl_2,KCl-CaCl_2-MgCl_2,KCl-NaCl-CeCl_3等三元相图.     

Thermodynamic modeling of the CeO2–CoO phase diagram

A thermodynamic modeling of the CeO₂–CoO phase diagram was performed with recent experimental data. The excess Gibbs energies of the solution phases were described on the basis of the simple regular solution. A consistent set of optimized interaction parameters was derived for describing the Gibbs energy of each phase in this system leading to a good fit between calculation and experimental data. The liquidus, solidus, and solvus curves were calculated and also the lattice stabilities of the components were evaluated.     

Phase-Field simulation of phase decomposition in Fe−Cr−Co alloy under an external magnetic field

Phase decomposition during isothermal aging of a Fe−Cr−Co ternary alloy under an external magnetic field is simulated based on the phase-field method. In this simulation, since the Gibbs energy available from the thermodynamic CALPHAD database of the equilibrium phase diagram is employed as a chemical free energy, the present calculation provides the quantitative microstructure changes directly linked to the phase diagram. The simulated microstructure evolution demonstrates that the lamella like microstructure elongated along the external magnetic field is evolved with the progress of aging. The morphological and temporal developments of the simulated microstructures are in good agreement with experimental results that have been obtained for this alloy system.     

Assessment of the Te-Tl (tellurium-thallium) system

The optimized thermodynamic data for the Te- TI binary system have been obtained by the computer operated least squares method from measured data. The Gibbs energy of the liquid phase was modeled as a two- sublattice model for ionic melt after Hillert.³¹ The intermediate compounds, Te₃Tl{2}and TeTl, were treated as stoichiometric phases, and the nonstoichiometric γ phase was expressed as a sublattice model. A strong tendency for chemical short- range order in the liquid state at the composition close to TeTh was confirmed by calculated results, but the existence of the TeTh phase was not justified. The experimental thermodynamic and phase diagram data were closely reproduced by the optimized thermodynamic data. Parameters describing the Gibbs energies of all the phases in this calculation and the calculated phase diagram and thermodynamic functions are presented and compared with experimental information.     

Assessment of the Te-Tl (tellurium-thallium) system

The optimized thermodynamic data for the Te- TI binary system have been obtained by the computer operated least squares method from measured data. The Gibbs energy of the liquid phase was modeled as a two- sublattice model for ionic melt after Hillert.³¹ The intermediate compounds, Te₃Tl{2}and TeTl, were treated as stoichiometric phases, and the nonstoichiometric γ phase was expressed as a sublattice model. A strong tendency for chemical short- range order in the liquid state at the composition close to TeTh was confirmed by calculated results, but the existence of the TeTh phase was not justified. The experimental thermodynamic and phase diagram data were closely reproduced by the optimized thermodynamic data. Parameters describing the Gibbs energies of all the phases in this calculation and the calculated phase diagram and thermodynamic functions are presented and compared with experimental information.     

Thermodynamic assessment of the Al-Pt binary system

The calculation of phase diagram (CALPHAD) technique has been used to carry out the thermodynamic assessment of the Al-Pt binary system. Seven intermetallics are considered as stable phases in addition to the terminal solid solutions. The set of Gibbs energy functions with optimized parameters is used to calculate the Al-Pt binary phase diagram as well as the thermodynamic properties in good agreement with the experimental results.     

Thermodynamic assessment of the Al-Pt binary system

The calculation of phase diagram (CALPHAD) technique has been used to carry out the thermodynamic assessment of the Al-Pt binary system. Seven intermetallics are considered as stable phases in addition to the terminal solid solutions. The set of Gibbs energy functions with optimized parameters is used to calculate the Al-Pt binary phase diagram as well as the thermodynamic properties in good agreement with the experimental results.     

基于Miedema模型和Toop模型的Al-Si-Er合金热力学参数计算

运用Miedema混合焓模型计算了Al-Er、Si-Er和Al-Si二元合金的部分热力学性质,选择Er为非对称性组元,在此基础上结合Toop模型计算出Al-Si-Er三元合金的混合焓、过剩熵与过剩自由能。结果表明,Al-Si-Er三元合金的混合焓、过剩熵与过剩自由能在整个浓度范围内均为负值,在富Er和贫Er区域各热力学参数变化趋势较大。通过计算Al、Si和Er 3种组元的偏摩尔过剩自由能得到Al-Si-Er三元合金各组元的等活度值曲线。曲线显示各组元随着摩尔分数的减少其活度值都急剧减小,在三元系成分三角形的中心部分Al、Si和Er的活度值都很小,这表明Al、Si和Er 3种组元之间存在很强的相互作用,易形成三元金属间化合物,这一结论与Al-Si-Er三元相图的实际情况相符合。     

A diffuse-interface model of reactive wetting with intermetallic formation

A diffuse-interface model of reactive wetting with intermetallic formation is developed that incorporates fluid flow, phase change and solute diffusion. The model is based on the total molar Gibbs energy of a ternary system with four phases. Numerical simulations were performed using a mesh-adaptive finite element method, revealing the complex behavior of the reactive wetting process. The model was verified against equilibrium states derived from the classical phase diagram and from interface energy considerations. Dynamic results show that the intermetallic can either precede or follow the spreading liquid droplet, depending on the time and the choice of interface energy and kinetic coefficients. Despite this difference, the spreading rate was not affected for the cases considered.     

Computer-aided thermodynamic study of solid Co---Pd alloys by Knudsen cell mass spectrometry, and calculation of the phase diagram

F.c.c. solid Co---Pd alloys have been investigated thermodynamically by means of computer-aided Knudsen cell mass spectrometry. Thermodynamic evaluation has been performed by applying the “digital intensity ratio” method. The thermodynamic excess properties can be described algebraically by means of thermodynamically adapted power series with two adjustable parameters, i.e. C₁^G (−20 810 + 9.608T) J mol⁻¹) and C₂^G (−30 720 + 6.78T) J mol⁻¹). At 1470 K, f.c.c. solid Co---Pd alloys are characterized by negative molar excess Gibbs energies G^E, exothermic molar heats of mixing (H^E) and small negative molar excess entropies S^E. At 1470 K, the minimum G^E value is −4600 J mol⁻¹ (61.9 at.% Pd), the minimum H^E value is −9400 J mol⁻¹ (59.5 at.% Pd) and the minimum S^E value is −3.3 J mol⁻¹ K⁻¹ (55.9 at.% Pd). The thermodynamic activities of Co show small positive deviations from the ideal case for the Co-rich alloys (x_Pd < 0.34), and negative deviations from Raoults' law for alloys with higher Pd contents. The Pd activities a_Pd show negative deviations from the ideal case for all compositions. The phase diagram has been computed by means of a generally applicable procedure for the calculation of the equilibrium compositions of coexisting phases. This was achieved using the results of this work, thermodynamic data from earlier mass spectrometric studies on the liquid phase, and literature data for the heat capacities and enthalpies of Co and Pd.     

Thermodynamic Assessment of Gd-Ni System

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Thermodynamic optimization of the AgCl-KCl and BaCl2-LiCl systems

The values of the thermodynamic properties of the liquid phase of the AgCl-KCl and BaCl₂-LiCl systems were optimized taking into account all the available experimental thermochemical and phase diagram information from the literature. Each liquid was described as a substitutional solution, and a Redlich-Kister formalism was used for the excess Gibbs energy.     

Thermodynamic Assessment of Dy-Co System

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Thermodynamic optimization of the AgCl-KCl and BaCl<Subscript>2</Subscript>-LiCl systems

The values of the thermodynamic properties of the liquid phase of the AgCl-KCl and BaCl₂-LiCl systems were optimized taking into account all the available experimental thermochemical and phase diagram information from the literature. Each liquid was described as a substitutional solution, and a Redlich-Kister formalism was used for the excess Gibbs energy.     

Application of Graham scan algorithm in binary phase diagram calculation

Graham scan, a computational geometric algorithm for finding a two-dimensional convex hull, is introduced to calculate binary phase diagrams. This algorithm is modified and applied to find the convex hull of discrete points in the space of Gibbs energy vs mol fraction. The modified Graham scan algorithm has a very low computational cost, which improves efficiency in binary phase diagram calculation.     

Thermodynamic reassessment of the Au–Te system

The Au–Te binary system has been thermodynamically reassessed using the CALPHALD method. The excess Gibbs energy of the liquid phase was formulated with the Redlich–Kister expression and the AuTe₂ intermetallic phase was treated as a stoichiometric compound. A set of self-consistent thermodynamic parameters for each phase has been obtained. Good agreement is reached between the calculated and experimental results. Additionally, the standard formation enthalpy and enthalpy of fusion of AuTe₂ intermetallic phase have also been calculated.     

A thermodynamic assessment of Ce-Al system

1 ＩｎｔｒｏｄｕｃｔｉｏｎＲＥ ＡｌａｎｄＲＥ Ａｌ Ｍｅａｒｅｐｏｔｅｎｔｉａｌａｍｏｒｐｈｏｕｓａｌｌｏｙ[1]ａｎｄｈｙｄｒｏｇｅｎ ａｂｓｏｒｂｉｎｇｍａｔｅｒｉａｌｓ[2 ].ＲａｒｅＥａｒｔｈ ,ａｓａｄｄｉｔｉｏｎａｌｅｌｅ ｍｅｎｔｓｉｎａｌｕｍｉｎｕｍａｎｄＡｌ ｔｒａｎｓｉｔｉｏｎｍｅｔａｌｓａｌｌｏｙ ,ｃａｎｉｍｐｒｏｖｅｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆｔｈｅｆｉｎａｌｍａｔｅｒｉａｌｓ[3].Ｔｈｅｐｈａｓｅｄｉａｇｒａｍａｎｄｔｈｅｒｍｏｄｙｎａｍｉｃｐｒｏｐｅｒｔｉｅｓｏｆｔ…     

Cluster/site approximation calculation of the ordering phase diagram for Cd–Mg alloys

We have used the modified cluster/site approximation in a phenomenological calculation of the phase diagram and single phase thermodynamic properties for cadmium–magnesium alloys in the order/disorder region. Values for the three cluster energies differ little from those obtained by LMTO-ASA calculations on unrelaxed alloys of ideal c/a ratio. Only two other parameters contained in contributions to the Gibbs energy are required. One comes from a configuration independent term and the other is an entropy factor coming from the cluster/site approximation.     

MgO-B2O3二元系熔渣质量作用浓度计算模型

依据化学中广泛应用的同系线性规律,拟合钙、镁复合化合物标准反应吉布斯自由能之间的线性关系式,然后由3CaO·B2O3和2CaO·B2O3的标准反应吉布斯自由能求得3MgO·B2O3和2MgO·B2O3的标准反应吉布斯自由能,进而基于炉渣结构的共存理论和相图,推导MgO-B2O3二元渣系的热力学计算模型.结果表明:1 460℃时,在浓度为0.45＜x(MgO)＜0.80的范围内,理论计算的MgO-B2O3渣系的作用浓度N(B2O3)的变化规律与实测活度α(B2O3)是相同的,且拟合较好.     

Solid-State Phase Equilibria of the Cu-S System: Thermodynamic Modeling

All phase equilibria and thermodynamic data available in the literature on the copper sulfides high- and low-temperature chalcocite, djurleite and anilite have been critically analyzed for optimization of the solid-state phase diagram of the Cu-S system at 1 bar total pressure. A two-sublattice approach derived from a recently developed Gibbs energy model for digenite enables the consideration of the solid solution nature of both modifications of chalcocite and for the first time of djurleite. Anilite is considered as stoichiometric compound. The sulfur solubility of metallic copper is described by a substitutional approach. The obtained Gibbs energy functions for high- and low-temperature chalcocite, djurleite, anilite and copper alloy phase allow computations and predictions of phase equilibria and thermodynamic properties in good accordance with experimental data of the Cu-S solid-state system.