Estimation of Thermodynamic Properties from Binary Phase Diagram

The general relationship between binary phase diagrams and the thermodynamic properties was system- atically derived without any assumption.A procedure was presented to estimate the thermodynamic proper- ties from the binary phase diagrams.

Thermodynamic modeling and phase diagram prediction of salt lake brine systems.Ⅰ. Aqueous Mg^2+–Ca^2+–Cl^- binary and ternary systems

Salt lake brine is a complex salt-water system under natural environment.Although many models can express the thermodynamic properties and phase equilibrium of electrolyte aqueous solution,the multi-temperature characteristics and predictability are still the goals of model development.In this study,a comprehensive thermodynamic model system is re-established based on the eNRTL model and some improvements:(1) new expression of long-range electrostatic term with symmetrical reference state is proposed to handle the electrolyte solution covering entire concentration range;(2) the temperature dependence of the binary interaction parameters is formulated with a Gibbs Helmholtz expression containing three temperature coefficients,the liquid parameters,which associated with Gibbs energy,enthalpy,and heat capacity contribution;and(3) liquid parameters and solid species data are regressed from properties and solubility data at full temperature range.Together the activity coefficient model,property models and parameters of liquid and solid offer a comprehensive thermodynamic model system for the typical bittern of MgCl2-CaCl2-H2 O binary and ternary systems,and it shows excellent agreement with the literature data for the ternary and binary systems.The successful prediction of complete phase diagram of ternary system shows that the model has the ability to deal with high concentration and high non-idealitv system,and the ability to extrapolate the temperature.

Thermodynamic modeling and phase diagram prediction of salt lake brine systemsⅡ.Aqueous Li^(+)-Na^(+)-K^(+)-SO_(4)^(2-) and its subsystems

It is still a challenging task to accurately and temperature-continuously express the thermodynamic properties and phase equilibrium behaviors of the salt-lake brine with multi-component,multitemperature and high concentration.The essential subsystem of sulfate type brine,aqueous Li^(+)-Na^(+)-K^(+)-SO_(4)^(2-) and its subsystems across a temperature range from 250 K to 643 K are investigated with the improved comprehensive thermodynamic model.Liquid parameters(Δg_(IJ),Δh_(IJ),and ΔC_(p,IJ))associated with the contributions of Gibbs energy,enthalpy,and heat capacity to the binary interaction parameters,i.e.the temperature coefficients of eNRTL parameters formulated with a Gibbs Helmholtz expression,are determined via multi-objective optimization method.The solid constantsΔ_(f)G_(k)°^((298.15))andΔ_(f)H_(k)°^((298.15))of11 solid species occurred in the quaternary system are rebuilt from multi-temperature solubilities.The modeling results show the accurate representation of(1)solution properties and binary phase diagram at temperature ranges from eutectic points to 643 K;(2)isothermal phase diagrams for Li_(2)SO_(4)-Na_(2)SO_(4)-H_(2)O,Li_(2)SO_(4)-K_(2)SO_(4)-H_(2)O and Na_(2)SO_(4)-K_(2)SO_(4)-H_(2)O ternary systems.The predicted results of complete structure and polythermal phase diagram of ternary systems and the isothermal phase diagrams of quaternary system excellently match with the experimental data.

Thermodynamic Optimization of TmCl_3-ACl (A=Na, K, Rb, Cs) Phase Diagrams

From the measured phase equilibria data and experimental thermochemical properties, the TmCl_3-ACl (A=Na, K, Rb, Cs) phase diagrams were optimized and calculated using the CALPHAD technique. For describing the Gibbs energies of the liquid phase in these systems, the new modified quasichemical model in the pair-approximation for short-range ordering was used. A set of thermodynamic functions was optimized and gotten based on an interactive computer-assisted analysis. The calculated phase diagrams and thermodynamic data are self-consistent.

Thermodynamic optimization and calculation of phase diagrams of YbCl_3-MCl (M=Na, K, Rb, Cs)

YbCl3-MCl （M = Na, K, Rb, Cs） systems were optimized and calculated using the CALPHAD （CALculation of PHAse Diagram） technique. The modified quasi-chemical model in the pair-approximation for short-range ordering was used to describe the Gibbs energies of liquid phase in the systems. On the basis of the measured phase diagram data and experimental thermodynamic properties, a series of thermodynamic functions were optimized and calculated through an interactive computer-assisted analysis. Furthermore, some reasonable discussions on the thermodynamic parameters for these strong interaction binary systems were carded out. The results showed that the optimized parameters and experimental data are thermodynamically self-consistent.

APPLICATION OF THE ANNEXATION PRINCIPLE TO THE STUDY OF THERMODYNAMIC PROPERTIES OF TERNARY METALLIC MELTS Cd-Pb-Sb

Based on the phase diagrams, measured activities and the annexation principle, the calculating models of mass action concentrations for Cd-Pb, Pb-Sb and Cd-Sb binary as well as Cd-Pb-Sb ternary metallic melts have been formulated. The results of calculation both agree with practice and obey the mass action law. This in turn testifies that the models formulated can reflect the structural reality of corresponding melts and the annexation principle is applicable to these melts.

New Asymmetric Model for Predicting Ternary Thermodynamic Properties

The prediction of the thermodynamic properties of ternary systems from the properties of their sub-binary systems is of great importance to phase diagram calculations. In the present study, a new asymmetric model which has more clear physical significance has been developed for evaluating the ternary thermodynamic properties from its three binary components. The model is considered to be rigorous in the case where the pseudobinary systems of fixed X2/X3 are regular are regular solution. The application of new model to the prediction of ternary enthalpies of mixing for Bi-Ga-Sn, Au-Ag-Sn and NaCl-KCl-CaCl2 systems shows that the calculated results by new model are closer to experimental data than those by Toop's model.

Phase diagram and thermodynamic properties of Ag-Cu alloys

Interactive laws of the components described by Gibbs energy functions of CC theory are different from each other, but each G-function can be used to draw the phase diagram of Ag-Cu system with almost the same accuracy. The partial molar properties of the components obtained from all these G-functions are identical. This shows the defects of thermodynamics of alloys. The thermodynamic properties of Ag-Cu alloys and their components have been calculated by the correct G-function which is chosen through a relative study of the energy, volume, atomic arrangement and electronic structure.

Thermodynamic assessment of ZnO-SiO_2 system

ZnO-containing slags are common in pyrometallurgical processing of the base metals and steel.This caused the interest to the thermodynamics of the ZnO-SiO2 system.A complete literature survey,critical evaluation of the available experimental data and a thermodynamic optimization of the phase equilibria and thermodynamic properties of the system ZnO-SiO2 at 1.013×105 Pa are presented.The molten oxide was described as an associate solution.The properties of liquid were reassessed and enthalpy term of the Gibbs energy of solid Zn2SiO4 was re-fitted to be compatible with the new data in the willemite primary phase field.The thermodynamic data set agrees well with the recent experimental observations.It can be used for predicting,e.g.,the thermodynamic properties and the domains of the phase diagram,like critical point of the liquid miscibility gap,with a better accuracy than using the previous assessments.A set of optimized model parameters were obtained,reproducing the reliable thermodynamic and phase equilibrium data within their experimental errors from 298 K to liquidus temperatures,over the entire composition range.The created database can be used in a Gibbs energy minimization software to calculate the thermodynamic properties and the phase diagram sections of interest.

Thermodynamic Assessment of Fe-Dy System

The phase diagram and thermodynamic data of the FeDy system were critically assessed by means of the computer programs THERMOCALC, using models for the Gibbs energies of individual phases. The system contains four intermetallic compounds. Good agreement is obtained between the calculation and experimental results.

A thermodynamic assessment of Ce-Al system

The optimized descriptions of the phase diagram and thermodynamic properties for Ce-Al system have been obtained from experimental thermodynamic and phase diagram data by means of the computer program THERMO-CALC based on the least squares method, using models for the Gibbs energy of individual phases. The system contains five intermetallic compounds. The calculated standard enthalpies of Ce_3Al, CeAl, CeAl_2, CeAl_3 and Ce_3Al_ 11 are -26.7, -48.9, -48.4, -44.0 and -41.7 kJ/mol, respectively. A consistent set of thermodynamic parameters was derived. The optimized and experimental data are in good agreement.

Thermodynamic optimization of the DyCl_3-KCl and DyCl_3-CaCl_2 systems

From the measured phase diagram data and experimental thermochemical properties, the DyCl3-KCl and DyCl3-CaCl2 phase diagrams were optimized and calculated by the CALPHAD technique. The Gibbs energies of liquid phase in the two systems has been optimized and calculated by new modified quasi-chemical model in the pair-approximation for short-range ordering, and a series of thermodynamic functions has also been optimized based on an interactive computer-assisted analysis. The results showed that the calculated phase diagrams and thermodynamic data were serf-consistent.

THERMODYNAMICS AND PHASE EQUILIBRIUM OF Cu－Y－O，Cu－Y－S，Cu－Y－O－S LIQUID SOLUTIONS

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Thermodynamic Assessment of the Pt-Sb System

The Pt-Sb system was critically assessed by means of CALPHAD technique. Based on the experimental data in the literature, the excess Gibbs energies of the solution phases (liquid, rhombohedral, fcc) were modeled with the Redlich-Kister equation. The five intermetallic compounds, Pt7Sb, Pt3Sb, Pt3Sb2, PtSb, and PtSb2 were treated as stochiometric compounds and expressed as the formula (Pt)m(Sb)n. The intermetallic compound, Pt5Sb with a homogenerity ranges 0.155 -?0.189 Sb, were treated as the formula (Pt,Sb)m(Pt,Sb)n. A set of self-consistent thermodynamic parameters of the Pt-Sb system was obtained.

Thermodynamics and Phase Equilibrium of Cu－Ce－O，Cu－Ce－S，Cu－Ce－O－S Liquid Solutions

Thermodynamics of Cu-Ce-O,Cu-Ce-S and Cu-Ce-0-S solutions at 1200℃ were studied by using solid electrolyte cell and chemical equilibrium method.The equilibrium constant of deoxidation,desulfurization and deoxysulfurization by Ce,the Gibbs standard reaction free energies of the formation of Ce_2O_3,CeS and Ce_2O_2S in Cu-base solution,activity interaction coefficients of S and Ce,temperature dependence of standard reaction free energy of solution of Ce in Cu,self-interaction coefficients of Ce in liquid Cu have been obtained.The phase precipitation diagram for Cu-CeS-O system has been plotted.The thermodynamic condition of the existence of Ce_2O_3,CeS and Ce_2O_2S in liquid Cu has been determined.It provides the basis for predicting the sequence and the type of equilibrium inclusions of Ce formed in Cu-base solution.

基于第一性原理和热力学计算的TiAl-Nb金属间化合物稳定性和相关系研究

采用基于广义梯度近似密度泛函理论的第一性原理计算和相图计算方法,研究了TiAl-Nb合金中γ、α_(2)、O_(2)和ωo相的热力学和力学性质以及相转变关系.研究表明,第一性原理计算得到的化合物相的参数是准确的,且分析结果与相图计算结果相一致.四个化合物相都是能够稳定存在的相.通过热力学和力学性质的分析,发现α_(2)相更容易转变为O_(2)相,并且在一定条件下可以通过相变反应生成ωo相.而γ相更容易转变为ωo相,但无法生成O_(2)相.

Prediction of the Gibbs Free Energies of Formation of Intermediate Compounds in a Binary System

A method for predicting the Gibbs free energies of intermediate compounds in a binary system has been presented, based upon the regulations of the Gibbs free energies of formation of intermediate compounds in the system. The application of this procedure to the V-O system demonstrates that this method is feasible.

Re-assessment and Optimization of the Ga-M (M=In, Sb,Pb) Systems with Chemsage

The thermodynamic properties and the phase diagrams of the systems Ga-M (M = In, Sb, Ph) were critically re-assessed and optimized employing the software package ChemSage for the calculation of thermodynamicequilibria. The Redlich-Kister/Margules formalism was employed for all solution phases and sets of self-consistentthermodynamic parameters were obtained. The results of re-assessment and optimization are compared with previous work, they are in excellent agreement with most experimental data.

KNO_(3)-NaNO_(2)-KNO_(2)三元系相图筛选及物性测试

为研发出与太阳能热发电技术相匹配的新型传/蓄热熔盐材料,选取KNO_(3)、NaNO_(2)和KNO_(2)作为研究对象,基于亚正规溶液模型对KNO_(3)-NaNO_(2)-KNO_(2)三元系相图展开热力学理论计算,同时采用相图软件FactSage 8.2对该体系相图进行模拟,结合试验确定体系共晶点,并对优选熔盐的储热能力进行研究。结果表明,采用亚正规溶液模型计算的三元熔盐的共晶点数据具有较高的准确性。优选出的混合熔盐的组成为42.0%KNO_(3)-48.5%NaNO_(2)-9.5%KNO_(2)(百分数为物质的量分数),实测熔点为139.8℃,熔化终止点为146.3℃,熔化热为71.1 J/g,分解温度为652.0℃,平均液态比热容约为1.48 J/(g∙K)。

Cu-Ce-O,Cu-Ce-S,Cu-Ce-O-S溶液体系热力学及其沉淀图

本文采用铜液与反应产物直接平衡法,并用固体电解质氧浓差电池和低温无水电解分离反应产物等技术,在1200℃研究了Cu—Ce-O,Cu—Ce-S,Cu—Ce-O—S溶液体系热力学得到了铜液中铈的脱氧、脱硫,脱硫氧常数和平衡产物Ce_2O_3,CeS,Ce_2O_2S的Gibbs标准生成自由能,Ce与S的活度相互作用系数以及Ce的标准溶解自由能和自作用系数与温度的关系式绘制了铜液中[Ce]-[S]-[O]平面沉淀图,确定了铜液中Ce_2O_3,CeS,Ce_2O_2S稳定存在的热力学条件。