Approximate thermodynamic solution phase data for steels

Approximate thermodynamic data based on a minimum amount of experiments are optimized for liquid, ferrite and austenite of some iron-based systems not assessed earlier, for a more accurate calculation of phase equilibria between these phases in multicomponent steels. The new data are shown to improve the correlation between calculated and measured liquidus temperature, solute partition and primary phase data in typical stainless steels.     

Thermodynamic optimization and calculation of the ErCl3–MCl (M=Li,Na,K,Rb,Cs ) systems

In this paper, the binary phase diagrams of the ErCl₃–MCl (M = Li, Na, K, Rb, Cs) systems were studied by the CALPHAD (CALculation of PHAse Diagram) approach. The modified quasi-chemical model in the pair-approximation for short-range ordering was used to describe the Gibbs energies of the liquid phase in the systems. From measured phase diagram data and experimental thermochemical properties, a series of thermodynamic functions has been optimized based on computer-assisted analysis. A discussion of thermodynamic functions for strong interaction binary systems was undertaken. The results showed that the calculated phase diagrams and optimized thermodynamic parameters are self-consistent.     

Thermodynamic description of solution phases of systems Fe-Cr-Si and Fe-Ni-Si with low silicon contents and with application to stainless steels

A thermodynamic optimization has been made for the solution phases of the ternary systems Fe-Cr-Si and Fe-Ni-Si in the iron-rich corner. Ternary substitutional-solution interaction parameters were optimized for the liquid, fcc and bcc phases, and the lower-order data were taken from the earlier assessed sub-systems. The calculated results were validated with experiments of phase equilibria and component activities in liquid. The new data were then added to the existing database of multicomponent steels and calculations were carried out for certain silicon containing stainless steels. As a result, clearly improved agreement was obtained between calculations and experiments concerning the liquidus temperatures and the solid/liquid partitioning of silicon in these steels.     

Phase field and level set methods for modeling solute precipitation and/or dissolution

The dynamics of solid–liquid interfaces controlled by solute precipitation and/or dissolution due to the chemical reaction at the interface were computed in two dimensions using a phase field models. Sharp-interface asymptotic analysis demonstrated that the phase field solutions should converge to the proper sharp-interface precipitation/dissolution limit. For the purpose of comparison, the numerical solution of the sharp-interface model for solute precipitation/dissolution was directly solved using a level set method. In general, the phase field results are found in good agreement with the level set results for all reaction rates and geometry configurations investigated. Present study supports the applications of both methods to more complicated and realistic reactive systems, including the nuclear waste release and mineral precipitation and dissolution.     

Implementation of variably saturated flow into PHREEQC for the simulation of biogeochemical reactions in the vadose zone

A software tool for the simulation of one-dimensional unsaturated flow and solute transport together with biogeochemical reactions in the vadose zone was developed by integrating a numerical solution of Richards' equation into the geochemical modelling framework PHREEQC. Unlike existing software, the new simulation tool is fully based on existing capabilities of PHREEQC without source code modifications or coupling to external software packages. Because of the direct integration, the full set of PHREEQC's geochemical reactions with connected databases for reaction constants is immediately accessible. Thus, unsaturated flow and solute transport can be simulated together with complex solution speciation, equilibrium and kinetic mineral reactions, redox reactions, ion exchange reactions and surface adsorption including diffuse double layer calculations. Liquid phase flow is solved as a result of element advection, where the Darcy flux is calculated according to Richards' equation. For accurate representation of advection-dominated transport, a total-variation-diminishing scheme was implemented. Dispersion was simulated with a standard approach; however, PHREEQC's multicomponent transport capabilities can be used to simulate species-dependent diffusion. Since liquid phase saturation is recalculated after every reaction step, biogeochemical processes that modify liquid phase saturation, such as dissolution or precipitation of hydrated minerals are considered a priori. Implementation of the numerical schemes for flow and solute transport have been described, along with examples of the extensive code verification, before illustrating more advanced application examples. These include (i) the simulation of infiltration with saturation-dependent cation exchange capacity, (ii) changes in hydraulic properties due to mineral reactions and (iii) transport of mobile organic substances with complexation of heavy metals in varying geochemical conditions.     

邻-二(吡咯-2-甲酰胺基)亚苯对卤素阴离子识别的密度泛函研究

采用密度泛函B3LYP/LanL2DZ方法优化了气相以及在四氢呋喃(THF)、甲醇及二甲亚砜(DMSO)3种溶剂中邻-二(吡咯-2-甲酰胺基)亚苯(DPCP)及其卤素阴离子复合物的几何构型。从几何结构、电荷布居、结合能以及热力学参数等角度探讨复合物形成过程中受体与阴离子间的相互作用。研究结果表明:复合物稳定性与卤素离子的种类和溶剂极性有关,同一溶剂中,复合物DPCP-X~-以DPCP-F~-最稳定,随着卤素离子半径的递增,稳定性逐渐下降,F~-,Cl~-在气相和3种溶剂中都能形成稳定的复合物,Br~-复合物只在气相稳定,在选定的3种溶剂中均不能形成稳定的复合物,而I~-无论在气相还是在3种溶剂中均不能形成稳定的复合物;同一复合物DPCP-X~-稳定性随溶剂极性的增大逐渐减小。利用相同的理论方法预测了在3种溶剂中DPCP与OH~-及CN~-的相互作用能力及复合物的稳定性。     

Optimization and calculation of the LaBr3–MBr (M=Na,K, Rb,Cs) phase diagrams

In this paper, the phase diagrams of the LaBr₃–MBr (M=Na, K, Rb, Cs) systems are optimized and calculated with the CALPHAD technique. The new modified quasi-chemical model in the pair approximation for local order was used to describe the Gibbs energies of the liquid in these systems. A set of thermodynamic functions has been optimized on the basis of an interactive computer-assisted analysis. The optimized thermodynamic parameters were used to calculate the thermodynamically self-consistent phase diagrams.     

用于柱层析的新型介电常数检测器研究

利用被分析/分离的有机化合物(溶质)与流动相(溶剂)的介电常数不同,则其浓度的变化将反映为溶液电容量的变化的特点,本文提出一种基于开关电容网络原理的微电容测量电路作为在线介电常数检测器.通过实验验证电路具有良好的灵敏度、线性度和温度稳定性.最后测量了多种有机溶液在不同浓度下的电容,表明电路输出电压与溶液浓度具有良好的线性关系.     

The Cd–Te phase diagram

The properties of the liquid phase in the Cd–Te system are fit using thermodynamic properties of CdTe(c) recently optimized by the author. These include a high temperature heat capacity significantly lower than commonly used such that the enthalpy of formation of CdTe(c) at its melting point is about 10 kJ/mol less negative than previously thought. An associated solution model with Cd, CdTe, and Te species is used. Seven adjustable parameters are sufficient to quantitatively fit the liquidus and partial pressures of Te₂ and Cd. Additional partial pressures for Te rich CdTe(c) near its melting point are extracted from an earlier study and tabulated. The parameters giving good fits to the liquidus and partial pressures give only a fair fit to the enthalpy of mixing of the liquid phase. Moreover, the parameters giving a good fit to the enthalpy give poor fits to the other data. The sensitivity of the different data types to changes in the interaction parameters of the associated solution model is established. A variation of ±160 J/g atom in the enthalpy parameter determining the CdTe–Te interaction is sufficient to double the fractional standard deviation between experimental and calculated partial pressures of Te₂ over Te rich CdTe(c) from 0.034 to 0.07. Because the degree of association is near its maximum, the measures of fit to the data are insensitive to changes in the parameters determining the Cd–Te interaction.     

Thermodynamic modeling of the molybdenum-boron system

A complete set of internally consistent thermochemical data for the molybdenumboron system has been produced through calculations which make use of available experimental data and the exact mathematical relationships between equilibrium thermodynamic properties and phase diagrams. These optimized data agree quite well with reported experimental results, and provide the first available thermodynamic information for the Mo-B liquid phase.     

Transportation of neutral solute in deformable,anisotropic, soft tissue

We present a three-dimensional framework for the transport of neutral solute through soft biological tissue, such as the articular cartilage, under different mechanical loading conditions. The tissue is modelled as a mixture of three phases, a hyperelastic, anisotropic solid matrix, an incompressible inviscid fluid and a solute. The formulation accounts for the anisotropic interaction between the solid and the interstitial water and incorporates the interaction between the solute and the solid matrix. Under the proper circumstances, our model simplifies to biphasic theory and classical convection diffusion.We find that the pressure gradient variation plays an important role in the neutral solute transport when the soft tissue is dynamically loaded, because of the low concentration of solute present in cartilage. A linear function is suggested for the ratio of friction coefficient between the solute and solid to the friction coefficient between the interstitial water and solid matrix. After validating our model with the experiments of Quinn et al. [T.M. Quinn, C. Studer, A.J. Grodzinsky, J.J. Meister, Preservation and analysis of nonequilibrium solute concentration distributions within mechanically compressed cartilage explants, J. Biochem. Biophys. Methods 52 (2) (2002) 83–95], a numerical study of different dynamic loading conditions on solute transport is carried out.     

Thermodynamic optimization of the As–S system

Literature review, critical assessment and thermodynamic modeling of the liquid and solid phases in the As–S system are presented. A set of optimized model parameters was obtained to reproduce previously published experimental data. The literature data included enthalpies of formation, heat capacity, vapor pressure and phase equilibrium data. A significant discrepancy among different sets of literature data was revealed. The model for the liquid phase was developed within the framework of the Modified Quasichemical Model (MQM) in pair approximation. The resulting set of model parameters was merged and tested within a larger multicomponent thermodynamic database for pyrometallurgical copper, lead and recycling industrial operations.     

Thermodynamic modeling of the Mg–Ge–Pb system

All available thermodynamic and phase diagram data of the Mg–Ge and Mg–Pb binary systems, and the Mg–Ge–Pb ternary system have been critically evaluated and all reliable data have been simultaneously optimized to obtain one set of model parameters for the Gibbs energies of the liquid and all solid phases as functions of composition and temperature. The liquid phase was modeled using the Modified Quasichemical Model in order to describe the strong ordering in Mg–Ge and Mg–Pb liquid. Mg₂Ge–Mg₂Pb solid solution phase was modeled with consideration of a solid miscibility gap. All calculations were performed using the FactSage thermochemical software.     

Critical thermodynamic evaluation and optimization of the Pb–Pr,Pb–Nd,Pb–Tb and Pb–Dy systems

All available experimental data on phase equilibria and thermodynamic properties of the Pb–Pr, Pb–Nd, Pb–Tb and Pb–Dy binary systems were reviewed and critically examined. A thermodynamic optimization of these systems is presented for the first time. A set of optimized model parameters for all solid stoichiometric compounds, terminal solid solutions and liquid phase was built to reproduce all available reliable thermodynamic properties and phase diagram data within experimental error limits. The Modified Quasichemical Model in the pair approximation was used to describe the thermodynamic properties of the liquid solution accurately. In view of the limited experimental phase diagram and thermodynamic data available for these systems, trends in the rare earth-lead and rare earth–tin systems were examined to estimate the missing information and evaluate whether the predictions are reasonable. Based on these trends, a predicted phase diagram for the Pb–Nd and Pb–Tb systems, which are not established to date, is presented.