Thermodynamic modeling of motlen salt solutions with multivalent cations having multiple coordination numbers

多组分体系的热力学和相平衡建模在当今具有重要的工业意义。冶金和化学工业通常使用热化学程序包来模拟化学反应和相平衡，以进行工艺开发。多组分多价盐体系广泛用于金属的生产和加工。铝电解、难熔金属涂层、下一代核反应堆、有希望生产钛的电解液都依赖于熔盐化学。多元盐体系的热力学和相平衡模拟包括将相的吉布斯能展开为T、P和组成的函数，并寻找全局能量极小值。吉布斯能量函数的模型参数是通过优化它们的值来获得的，以最好地同时再现文献中的实验数据(热、液相线等)。参数形成数据库，模型用于预测多组分体系的相平衡和热力学性质。Gibbs能量模型必须符合多组分熔体的离子结构(氧化态和离子配位)，特别是对于溶解具有可变价阳离子的复杂的氯氟化物熔体，如NaF-KF-NaCl-KCl-TiFx-TiClx(x=2，3，4)体系。拟议的项目包括开发模型和参数数据库，用于预测具有工业意义的多组分互反盐体系的相平衡(液相线和共晶温度、稳定产物、蒸汽压)和热力学性质(活度、热焓、Cp)，其新颖之处在于考虑到离子的配位数和氧化态随着组成的变化。将为NaF-KF-NaCl-KCl-TiF2-TiCl2-TiF3-TiCl3-TiF4-TiCl4和AF-BeF2-ThF4-UF3-UF4-UF6(其中A是碱)体系开发模型。固体溶液和纯化合物也将被整合到模型中。对于液态溶液，钛和铀将有几个配位数(4-8)，它们与组成的相对稳定性将通过测量进行标定。

Thermodynamic and phase equilibrium modeling of multicomponent systems is of great industrial importance nowadays. The metallurgical and chemical industries commonly use thermochemical packages to simulate chemical reactions and phase equilibria for process development. Multicomponent multivalent salts systems are widely used for the production and processing of metals. Al electrolysis, coating of refractory metals, the next generation of nuclear reactors, promising electrolytes for Ti production all depend on molten salt chemistry. The thermodynamic and phase equilibrium modeling of multicomponent salt systems consists in expanding the Gibbs energy of a phase as a function of T, P and composition and finding a global energy minimum. Model parameters of the Gibbs energy functions are obtained by optimizing their values to best reproduce simultaneously the experimental data found in the literature (enthalpy, liquidus, etc.). Parameters form a database and the models are used to predict phase equilibria and thermodynamic properties in the multicomponent system. The Gibbs energy models must agree with the ionic structure of the multicomponent melt (oxidation states and coordination of ions), especially for complex chloro-fluoride melts dissolving some oxide components with cations of variables valency as the NaF-KF-NaCl-KCl-TiFx-TiClx (x=2, 3, 4) system. The proposed project consists in developing models and databases of parameters for the prediction of phase equilibria (liquidus and eutectic temperatures, stable products, vapor pressures) and thermodynamic properties (activities, enthalpy, Cp) of multicomponent reciprocal salts systems of industrial importance, with the novelty of taking into account the coordination numbers and oxidation states of the ions as they changes with composition. Models will be developed for the NaF-KF-NaCl-KCl-TiF2-TiCl2-TiF3 -TiCl3-TiF4-TiCl4 and the AF-BeF2-ThF4-UF3-UF4-UF6 (where A is an alkali) systems. Solid solutions and pure compounds will also be integrated in the model. For the liquid solution, Ti and U will have several coordination numbers (4-8) and their relative stabilities with composition will be calibrated on measurements.