二组分体系的相图及其相图边界理论

主要探讨了二组分体系的相图,如气-液相图和液-固相图,总结了二组分相图的分类、绘制及相图分析,这有利于理解和掌握二组分相图的基本规律。并简单介绍了相图边界理论,扩展了相图的热力学研究。     

二组分平衡体系的T-x相图

主要从3个方面介绍了二组分平衡体系的T-x相图。一是简单相图的介绍;二是简单相图的组合;三是实际体系复杂相图的认识。从而可以让学生理解和掌握相平衡中的二组分体系的气-液、液-液和液-固平衡的T-x相图,并为实际应用打下良好的基础。     

二组分典型系统相图的演变规律及其应用

分析了二组分典型系统的溶解性变化引起相图的演变规律,同时应用于实际教学中,达到了既可减少课堂授课时间,又可使学生较好地掌握各类典型相图特点和变化规律的目的。     

乙腈-水的液液、固液相平衡和过量Gibbs自由能

测制了xCH~3CN+(1-x)H~2O的液液、固液平衡相图, 此系液液分层的简单低共熔混合物类相图。低共熔点温度为227.44K, 组成x=0.955。最高临界溶解温度为271.0K, 临界组成x=0.35, 临界指数n=2.64。两液相与冰的平衡温度为263.07K。计算出体系在263.07K的过量Gibbs自由能G~m^E, 液液分层时G~m^E的最大值为1174J·mol^-^1。     

多元气-液-固复杂体系相平衡

石油流体中含有气相、液相及可能遇到的固相包括水合物、石蜡和沥青质等,涉及多元气-液-固复杂体系的相平衡问题.为防止这些沉积物堵塞造成安全隐患,需要确定水合物、石蜡、沥青质沉积起始条件以及沉积量.本文针对化学热力学理论在含水合物、石蜡和沥青质的多元-多相平衡研究中的应用进行了综述.水合物相平衡模型较为成熟,主要有两类,其一为基于等温吸附理论的van der Waals-Platteeuw型热力学模型;其二为基于双过程水合物生成机理的Chen-Guo水合物热力学模型.石蜡沉积一般采用活度系数法、状态方程法及多固相模型描述.沥青质絮凝、沉积则可采用溶解度参数模型、状态方程法、胶体模型和标度理论模型进行计算.同时对多元气-液-固复杂体系的相平衡研究发展方向进行了展望.     

推荐一个绿色化学实验——乙酸正丁酯-乙醇-水三组分液-液平衡相图测绘

介绍了部分互溶的液一液三组分新体系——乙酸正丁酯-乙醇-水的平衡相图实验方法、绘制及此实验体系在实验教学中的实验效果。可以利用该实验向学生渗透绿色化学的理念。     

5-磺基水杨酸固液相平衡研究

采用动态法测定了5-磺基水杨酸在甲醇、乙醇、正丙醇、正丁醇和水中的溶解度,并采用Van't Hoff方程、Apelblat方程与λh方程对溶解度数据进行关联,结果表明,5-磺基水杨酸在五种溶剂中的溶解度均随温度的升高而增大,在甲醇中的溶解度最大、水中最小,实验中的二元体系的关联结果与实验值相吻合,为5-磺基水杨酸纯化工...     

物理化学的互动-探究式教学研究——以二组分理想溶液系统的气、液平衡的讲授为例

在二组分理想溶液系统的气、液平衡的教学中运用了互动-探究的教学法,具体教学过程为:制定互动-探究的教学目标;通过设置互动环节,启迪学生深层次学习;通过对比分析,探讨结论,采用互动-探究式教学,能深刻挖掘所学内容在基本概念、基本理论方面的生长点等,取得了非常好的教学效果。     

邻位与对位二取代苯的二元液固平衡相图研究

用热分析法仔细地测定了邻、对位氯甲苯和邻、对位硝基氯苯两个系统在不同组成时的步冷曲线,并进行了结晶试验,从而确认它们都属于简单的低共熔型相图,而不是一个有最低凝固点的完全互溶固溶体相图。文中还根据这类异构物的物理和热力学特性,解释了实验观察到的相图特征。     

压力和温度对水型相图平衡影响的探讨

重点从热力学原理的角度探讨压力和温度对水型相图平衡的影响,并通过计算解释了水型相图中固液平衡线上随压力升高,熔点下降的原因。     

V-H2O体系的溶解组分优势区域图和电势-pH 图

运用浓度比较法, 对25 ℃时V-H2O体系进行热力学分析和电化学分析, 编程计算出各溶解组分浓度, 以及固相和液相、各固相间边界线, 确定固相区和液相区的位置. 在此基础上, 绘制出了总V浓度cT(V)=1.0×10-5 mol·L-1时V-H2O体系的溶解组分优势区域图和电势-pH图以及cT(V)=1.0×10-7 mol·L-1时V-H2O体系的电势-pH图. 电势-pH图结果表明在一定温度和压力下, 各相稳定区取决于体系中溶液态物质的总浓度. 随cT(V)的减小, 溶液稳定区增大, 各固相稳定区均不同程度减小.     

Determination of Phase Stability of Elemental Boron

Boron is an important element, used in applications from superhard materials to superconductors. Boron exists in several forms (allotropes) and, surprisingly, it was not known which form (α or β) is stable at ambient conditions. Through experiment, we quantify the relative stability of α‐boron and β‐boron as a function of temperature. The ground‐state energies of α‐boron and β‐boron are nearly identical. For all temperatures up to 2000 K, the complicated β‐boron structure is more stable than the simpler α‐boron structure at ambient pressure. Below 1000 K, β‐boron is entropically stabilized with respect to α‐boron owing to its partially occupied sites, whereas at higher temperatures β‐boron is enthalpically stabilized with respect to α‐boron. We show that α‐boron only becomes stable on application of pressure.     

Determination of High Pressure Phase Diagrams of the Ternary Alloy System

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Thermodynamic Study of the Solid-Liquid Equilibria in the Systems MIPO3-Pr(PO3)3 (MI=Na,Rb, Cs OR Ag)

A previously established equation of a stoichiometric phase liquidus curve was applied to determination of the phase diagrams of the systems M^IPO₃-Pr(PO₃)₃ (with M^I=Na, Rb, Cs or Ag). The temperature, enthalpy and entropy of fusion were calculated for each solid phase with the exception of silver polyphosphate, the crystallization field of which was very limited. The enthalpy of fusion of the polyphosphate Pr(PO₃)₃ was determined from the DTA curve. The melting enthalpy of Pr(PO₃)₃ calculated from the different binary systems was approximately equal to the measured value. The calculated temperatures and compositions were in good agreement with those determined experimentally. This revised version was published online in July 2006 with corrections to the Cover Date.     

Equilibrium Phase Diagrams of Interpenetrating Polymer Networks and Liquid Crystals

Summary: Swelling and deswelling of photochemically crosslinked interpenetrating polymer networks in anisotropic solvents were examined. Phase diagrams were established in terms of composition and temperature using two low-molecular-weight nematic liquid crystals, 4-cyano-4-n'-pentylbiphenyl and an eutectic mixture of cyanoparaphenylenes. Networks were formed by ultraviolet curing in the presence of a difunctional monomer and a photoinitiator. Immersion in excess of solvent allowed us to measure the solvent uptake by weight and to determine the size increase by optical microscopy in terms of temperature. We calculated weight and diameter ratios considering the swollen-to-dry network states of the samples.