Hydrate dissociation conditions for gas mixtures containing carbon dioxide, hydrogen, hydrogen sulfide, nitrogen, and hydrocarbons using SAFT

A new method, a molecular thermodynamic model based on statistical mechanics, is employed to predict the hydrate dissociation conditions for binary gas mixtures with carbon dioxide, hydrogen, hydrogen sulfide, nitrogen, and hydrocarbons in the presence of aqueous solutions. The statistical associating fluid theory (SAFT) equation of state is employed to characterize the vapor and liquid phases and the statistical model of van der Waals and Platteeuw for the hydrate phase. The predictions of the proposed model were found to be in satisfactory to excellent agreement with the experimental data.

Phase equilibria and plate-fluid interfacial tensions for associating hard sphere fluids confined in slit pores

The excess Helmholtz free energy functional for associating hard sphere fluid is formulated by using a modified fundamental measure theory [Y. X. Yu and J. Z. Wu, J. Chem. Phys. 117, 10156 (2002)]. Within the framework of density functional theory, the thermodynamic properties including phase equilibria for both molecules and monomers, equilibrium plate-fluid interfacial tensions and isotherms of excess adsorption, average molecule density, average monomer density, and plate-fluid interfacial tension for four-site associating hard sphere fluids confined in slit pores are investigated. The phase equilibria inside the hard slit pores and attractive slit pores are determined according to the requirement that temperature, chemical potential, and grand potential in coexistence phases should be equal and the plate-fluid interfacial tensions at equilibrium states are predicted consequently. The influences of association energy, fluid-solid interaction, and pore width on phase equilibria and equilibrium plate-fluid interfacial tensions are discussed.

Formation and Properties of a Novel Heavy-Metal Chalcogenide Glass Doped with a High Dysprosium Concentration

A novel heavy-metal chalcogenide glass doped with a high dysprosium ion (Dy(3+)) concentration was prepared by the well-established melt-quenching technique from high-purity elements. The results show that when Cadmium (Cd) is introduced into chalcogenide glass, the concentration of Dy(3+) ions doped in GeGaCdS glasses is markedly increased, the thermodynamic performance improves, and the difference between T(g) and T(x) is >120 degrees C. The Vickers microhardness is also modified greatly, about 245 kgf/mm(2). The optical spectra indicate that all absorption and emission bands of Dy(3+) are clearly observed and red-shifted with increasing Dy(3+) concentration.

钇和镧系元素萃取热力学及双水相体系分离氨基酸的研究

本文研究了一种中性萃取剂支链三烷基氧化膦（Cyanex 925）和一种羧酸类萃取剂仲辛基苯氧基取代乙酸（CA-12）萃取稀土元素和钇的热力学性能。探讨了利用CA -12为萃取剂将钇与其他稀土分离的可行性，遵循基础－应用的原则，完成了从龙南离子型矿的浸出液中提取钇的分馏串级模拟实验。在此基础上还进一步研究了“绿色溶剂”离子液为溶剂，CA-12萃取稀土和钇的热力学机理。我们还考察了双水相中氨基酸的分离，为利用双水相体系萃取稀土元素奠定了一定的基础。具体的研究内容如下： 1.系统的研究了Cyanex 925在硝酸体系中萃取稀土和Y的规律，由斜率分析方法确定了反应机理，发现了明显的四分组效应，并确定了Y在萃取中所处的位置。同时发现Cyanex 925有可能用于轻、重稀土分组，易反萃。 2.CA-12对Y萃取具有高的选择性，研究了Y与其他稀土分离的可能性。进行了CA-12从混合稀土中提取Y的工艺模拟实验，并获得纯度为99.5％Y2O3，该工艺高效简便，具有好的应用前景。 3.系统的研究了离子液作为溶剂，CA-12从硝酸介质中萃取稀土和Y的规律。考察了不同水相酸度、水相中相关各种离子及萃取剂浓度变化对CA-12萃取稀土和钇的影响，从而推导了萃取反应方程式及机理。并发现在同样萃取剂浓度和水相条件下，CA-12-离子液体系中萃取稀土和钇的能力低于CA-12-庚烷体系中。 4.研究了赖氨酸、蛋氨酸、苯丙氨酸和半胱氨酸在聚乙二醇（PEG）－磷酸盐双水相体系（ATPSs）中分配行为，分别考察了PEG分子量、水相pH、氨基酸侧链结构等对分配比的影响，得出氨基酸在双水相中的分配行为取决于双水相体系的性质和氨基酸的支链结构与带电情况。

DEHEDP的界面性质及其萃取分离稀土的热力学和动力学研究

本文系统研究了一种中性有机磷酸酷2一乙基己基麟酸二（2一乙基己基）酉旨（DEHEHP）从硝酸体系中萃取Ce~(4+)和F~-的热力学和动力学机理，并对该萃取剂的界面活性进行了深入的研究。在此基础上，探讨了钟（IV）与其他稀土和针分离的可能性，从理论上系统地研究了盐析剂存在下DEHEHP作为萃取剂对三价稀土（RE~(3+)）的萃取规律，并遵循基础一应用的原则，完成了从氟碳饰矿的硝酸浸出液中提取四价饰的分馏串级萃取模拟实验。此外，我们也研究了DEHEHP与酸性鳌合萃取剂HPMBP的混合体系对RE~(3+)的协萃效应。基于上述研究，评估了DEHEHP在稀土萃取领域的潜在的应用前景。具体的研究内容如下：1．模拟氟碳钟矿硝酸浸出液，系统研究了复杂体系中DEHEHP萃取Ce（IV）和F（I）的热力学机理，推导了萃取反应方程式及其机理，硼酸的加入，既不被萃取，也不影响饰和氟的萃取。2．DEHEHP作为硝酸体系中饰（IV）的良好萃取剂，研究了饰（IV）与其他稀土和针分离的可能性。在此基础上，进行了DEHEHP从含F（I）、Ce（IV）的硝酸稀土溶液中提取Ce（W）的工艺模拟实验，并获得纯度为99.9-99.99％CeO_2，饰产品中ThO_2/CeO_2<10~(-4)，该工艺高效简便，具有很好的应用前景。3．系统研究了在盐析剂存在下，DEHEHP从硝酸介质中萃取RE~(3+)的规律，发现了明显的四分组效应，并确定了Y在萃取系列中所处的位置，而Sc的萃取能力远远高于其它稀土元素。4．用层流恒界面池研究了DEHEHP萃取Ce（IV）和F（I）的传质动力学模式，考察了多种因素对萃取速率的影响，提出了水相化学反应机理，这与DEHEHP的界面活性有关，并且发现氟的存在，降低了钟的萃取速率。5．系统研究了各种因素对DEHEHP界面活性的影响，定性探讨了萃取剂界面活性与萃取动力学的关系，为萃取动力学传质模式的推导提供了辅助依据。6．考察了DEHEHP与酸性鳌合萃取剂HPMBP的混合体系分别在盐酸和硝酸介质中对RE~(3+)（包括Y~(3+)）的萃取和分离，得出了协萃反应方程式和平衡常数，并计算了相邻稀土元素间的分离因素，讨论了此混合体系对部分稀土分组或两两分离的可能性。

GROWTH OF WIDE-BAND GAP IMMISCIBLE II-VI ALLOYS BY METALORGANIC VAPOR-PHASE EPITAXY

Although metalorganic vapor phase epitaxy (MOVPE) is generally regarded as a non-equillibrium process, it can be assumed that a chemical equilibrium is established at the vapor-solid interface in the diffusion limited region of growth rate. In this paper, an equilibrium model was proposed to calculate the relation between vapor and solid compositions for II-VI ternary alloys. Metastable alloys in the miscibility gap may not be obtained when the growth temperature is lower than the critical temperature of the system. The influence of growth temperature, reactor pressure, input VI/II ratio, and input composition of group VI reactants has been calculated for ZnSSe, ZnSeTe and ZnSTe. The results are compared with experimental data for the ZnSSe and ZnSTe systems.

GROWTH OF GASB AND GAASSB IN THE SINGLE-PHASE REGION BY MOVPE

GaSb layers are grown on GaSb substrates; the effects of input partial pressure of trimethylantimony and the V/III ratio are studied. A model of the MOVPE phase diagram for the growth of GaSb and GaAsxSb1-x is developed which assumes thermodynamic equilibrium to be established at the solid-vapor interface.

Phase diagrams for the MOVPE growth of ZnTe and ZnSeTe

The phase diagrams for the MOVPE growth of ZnTe and ZnSeTe have been proposed for the first time, based on the thermodynamic equilibrium established at the solid-vapor interface, The regions for the single condensed phase of ZnTe(s) and of ZnSeTe(s) have been investigated, respectively, Additionally, the growth conditions of appearance for the double condensed phase of ZnTe(s) + Zn(s or l) and ZnTe(s)+ Te(s or l) for the ZnTe system, of ZnSeTe(s) + Zn(s or l) and ZnSeTe(s)+ Te(s or l) for the ZnSeTe system are discussed.

Molecular dynamics simulation of entropy and surface tension for grain boundary of α-Fe

The grain boundary is an interface and the surface tension is one of its important thermodynamic properties. In this paper, the surface tension of the ∑9 grain boundary for α-Fe at various temperatures and pressures is calculated by means of Computer Molecular Dynamics (CMD). The results agree satisfactorily with the experimental data. It is shown that the contribution of entropy to surface tension of grain boundary can be ignored.

Interface energy and its influence on interface fracture between metal and ceramic thin films in nanoscale

A theoretical model about the size-dependent interface energy between two thin films with different materials is developed by considering the chemical bonding contribution based on the thermodynamic expressions and the structure strain contribution based on the mechanical characteristics. The interface energy decreases with reducing thickness of thin films, and is determined by such available thermodynamic and mechanical parameters as the melting entropy, the melting enthalpy, the shear modulus of two materials, etc. The predicted interface energies of some metal/MgO and metal/Al2O3 interfaces based on the model are consistent with the results based on the molecular mechanics calculation. Furthermore, the interface fracture properties of Ag/MgO and Ni/Al2O3 based on the atomistic simulation are further compared with each other. The fracture strength and the toughness of the interface with the smaller structure interface energy are both found to be lower. The intrinsic relations among the interface energy, the interface strength, and the fracture toughness are discussed by introducing the related interface potential and the interface stress. The microscopic interface fracture toughness is found to equal the structure interface energy in nanoscale, and the microscopic fracture strength is proportional to the fracture toughness. (C) 2010 American Institute of Physics. [doi:10.1063/1.3501090]

A method to calculate the surface tension of a cylindrical droplet

The history of Laplace's equations for spherical and cylindrical droplets and the concept of dividing surface in Gibbs' thermodynamic theory of capillary phenomena are briefly reviewed. The existing theories of surface tensions of cylindrical droplets are briefly reviewed too. For cylindrical droplets, a new method to calculate the radius and the surface tension of the surface of tension is given. This method is suitable to be used by molecular dynamics simulations.