Pb-Al二元体系液-固界面自由能的热力学理论计算

以复杂的Warren二元及赝二元常规系统下的液-固界面自由能理论为基础, 借助Pb-Al二元体系为例对其进行简化, 获得了二元非混溶体系液-固界面自由能物理模型, 然后对其热力学公式进行推导, 得出只含两个参变量的理论公式, 并对几种温度下液-固界面自由能(γSL)计算值及用多相平衡(MPE)法得到的实验值作了对比. 结果表明, 改进的物理模型及理论公式易于理解、计算简便, γSL的计算值取决于温度及Al原子分数的两个参变量, 与实验值较好地吻合, 证明了该模型具有结构简单、精度较高的优点, 并可作为其它非混溶体系γSL的计算模型, 为其推广应用奠定基础.     

碳氢化合物燃烧中间体Lennard-Jones系数的计算

在已有的基团贡献法公式的基础上,提出了一种新的基团贡献法公式,并通过拟合250种化合物(包括185种稳定化合物临界性质的实验值和65种自由基临界性质的计算值)的临界性质得到了40种基团的贡献值,并用于预测未知化合物的临界性质.选取了训练集以外的、有临界性质实验值的30种化合物作为独立测试集,用于验证所建模型对临界性质的预测能力,T_C和P_C平均绝对偏差分别为8.52%和16.83%.结果表明,预测结果和实验值相吻合,该模型可以用于大分子化合物及自由基的临界性质预测.根据临界性质与Lennard-Jones(L-J)系数的经验关系式,预测了碳氢化合物燃烧中间体的L-J系数,得到独立测试集46种碳氢化合物的L-J系数,与文献值接近,T_C和P_C的平均绝对偏差分别为9.88%和9.96%.比较了训练集中烷烃自由基·C_6H_(13)、烯烃自由基·C_5H_9和炔烃自由基·C_5H_7同分异构体的L-J系数,同时,将己烷自由基·C_6H_(13)与相似的邻近烷烃C_6H_(14)的L-J系数进行比较,发现同分异构体之间或相似化合物之间L-J系数有较大偏差.此外,对缺少L-J系数的114种常见碳氢化合物自由基进行了预测.这对于碳氢化合物的燃烧模拟及基元反应中压强相关的速率常数计算有重要意义.     

多元Gd(Tb)-Ni-Al合金系中非晶形成能力的成分依赖性研究

采用水冷铜模吸铸法制备了Gd(Tb)-Ni-Al合金系样品.利用X射线衍射仪(XRD),示差扫描量热仪(DSC)和差热分析仪(DTA)分别检测了合金的结构,玻璃转变,晶化和合金的熔化行为.用γ参数来表征Gd基大块金属玻璃的非晶形成能力.结果表明,多元Gd基合金的非晶形成能力对Tb有较大的依赖性,15%Tb替换Gd57Ni20Al23合金中的Gd元素提高了Gd系合金的非晶形成能力,并应用等效电负性差(Δx)和等效原子半径差(δ)讨论了该系列合金的本征非晶形成能力.     

用瞬态形核理论研究钕对快凝Al-Fe-V-Si合金非晶形成倾向的影响

利用与时间有关的瞬态形核理论计算了不同Ｎｄ含量的Ａｅ－Ｖ－Ｓｉ－Ｎｄ合金中α－Ａｌ相的形核率、形核孕育期与过冷度的关系，并计算了α－Ａ１形成非晶的临界冷却速率。结果表明，随Ｎｄ含量增加，合金的液相线温度提高，α－Ａ１形核孕育期延长，形核过冷度增加，形核率降低临界冷却速率降低，从而增大其非晶的形成倾向。     

一级相变磁制冷材料LaFe_(11.6)Si_(1.4)合金的磁相变特性系统分析

以La Fe11.6Si1.4合金为研究对象,系统分析了该一级相变材料的居里温度(TC)、磁场诱导磁相变的临界磁场(HC)、磁化率(χ)、磁滞、磁熵变(ΔS)、制冷能力(RCP)等磁性特性。结果表明:温度诱导磁相变的居里温度和磁场诱导磁相变的临界磁场均随磁场呈线性增加,ΔTC和ΔH随磁场和温度的变化率的值分别为4.1 K·T-1和0.2 T·K-1。当合金处于纯铁磁态和顺磁态时熵变磁熵变几乎为零,但磁场诱导的磁相变,会导致某一定温度下合金磁熵变有一个突变。但合金最大熵变并不是随磁场的增加而线性增加,当磁场达到一定值后随磁场增加其值基本没有变化。不同模型计算的制冷能力均随磁场的增加而呈线性增加。在两相共存态中,同一温度下两种不同铁磁的磁化率存在差异,即因磁场诱导的铁磁态相与合金中本身的铁磁态相的磁化率存在差异,且前者小于后者,这种物理现象对深入研究温度诱导和磁场诱导磁相变的差异有一定的参考价值。     

玻璃硅烷化处理对罗丹明6G和亚甲基蓝吸附行为的影响

利用六甲基二硅烷胺对平面玻璃光波导(高折射率透明导光薄膜介质)进行硅烷化处理, 得到水接触角大于90°的疏水表面. 然后使用时间分辨光波导分光光谱技术研究水溶液中的罗丹明6G (R6G)和亚甲基蓝(MB)分子在疏水玻璃表面的吸附行为, 并与亲水玻璃条件下测得的结果进行对比. 对利用疏水玻璃光波导测得的R6G的吸附-脱附动力学曲线进行Langmuir拟合得到了R6G的吸附速率常数, 脱附速率常数以及吸附自由能. 并且发现与亲水玻璃情况相比, 吸附速率常数增大, 脱附速率常数减小, 吸附自由能更负. 在疏水玻璃表面形成的R6G和MB吸附层的吸光度与亲水玻璃情况相比显著升高, 表明这两种分子更倾向于吸附在疏水玻璃表面. 实验结果还发现玻璃硅烷化处理能够有效抑制这两种染料分子在表面的聚合反应.     

玻璃电极的校准方法

采用线性滴定法来求酸碱滴定终点时,要求提供一组能反映溶液中真实pH值的实验数据。但因某些玻璃电极本身性能的限制,使测出的pH值误差较大,不能满足线性滴定法对实验数据的精度要求。本文提出用三种标准缓冲溶液对饱和甘汞-玻璃电极体系进行校准,采用最小二乘法计算校正值的方法,可获得较高精度的pH值。     

恒温式量热计冷却校正公式的进一步研究

通过对参数“α”影响热值误差的理论分析,剖析了研究新的最佳冷却校正公式的途径和方向。据此,在前文提出两个新公式的基础上,进一步提出了一个改进的“α”值计算模型,并由电算求解列出“α”值计算表。从大量数据验证来看,它可能成为迄今为止国内外所见到的近似冷却校正公式中的优秀者,它兼具操作最简便,准确度仅次于最准确的Regnault-Pfaundler 公式的两个特点。     

铑(Ⅰ)催化烯烃碳酰化反应机理:手性聚稠环过程的对映选择性

采用密度泛函理论方法研究了[Rh(R,R-DIOP)]+[DIOP=(1R,2R)-1,2-O-异丙叉-1,2-二醚氧基-1,2-双(二苯基磷基)乙烷]催化下苯并环丁酮手性聚稠环过程在气相、四氢乙呋喃(THF)及水中的反应机理.计算结果表明,在气相中反应容易进行,经TS2形成六元环的过程为决速步骤,但产物无明显的对映选择性.在THF中,S-和R-通道的C—C键活化能垒仅由79.5和69.3 kJ/mol提高到80.2和88.8 kJ/mol,未改变反应的实质;Rh与2个C原子的配位明显弱于气相,相对于催化剂和反应物自由能之和,S-和R-通道的反应总能垒分别提高到63.8和68.1 kJ/mol.对于S-通道,溶剂THF使经TS2的能垒升至112.0 kJ/mol,仍为整个过程的决速步骤;然而对R-通道,溶剂使经TS1形成五元环过程的能垒升至91.5 kJ/mol,但使经TS2的能垒由78.9 kJ/mol降至77.7 kJ/mol,IM1→TS1成为决速步骤.在以水为溶剂时,经TS1形成五元环的过程成为2个通道的决速步骤,其在S-和R-通道中的能垒分别为102.5和94.9 kJ/mol.因此,溶剂改变了反应的决速步骤及能垒.3种方法均预测R-通道为主反应路径,但THF能明显增加产物的对映选择性.采用自然键轨道(NBO)电荷分析了反应过程中电荷的变化.     

类硅烯H_2SiLiF二聚反应的理论研究

从理论上研究了类硅烯H2SiLiF的三元环构型为反应物的二聚反应2H2SiLiF→H2SiSiH2+2LiF。在MP2/6-31G(d)和QCISD(T)/6-31G(d)水平下的计算结果表明,H2SiLiF的二聚反应经过两个阶段:阶段I,先形成过渡态TS1,经过中间体Int,形成一个四元环的中间产物Pro1,同时消去一个LiF;阶段Ⅱ,Pro1继续反应形成过渡态TS2,进而解离生成产物H2SiSiH2和一个LiF。从能量上看,反应易停留在中间产物阶段。本文对反应物、过渡态以及产物的结构、稳定性等方面进行了讨论,很好解释了实验结果。     

Measurement and prediction of binary mixture flash point

The flash points of three binary mixtures, containing n-heptane, o-xylene, m-xylene and ethylbenzene, were measured by Pensky-Martens closed cup tester. The experimental data were compared with the calculated values using Liaw’s Model with the application of Raoult’s Law and Wilson equation. These equations were in good qualitative agreement.     

Isothermal (vapour + liquid) equilibrium for binary mixtures of polyethylene glycol mono-4-nonylphenyl ether (PEGNPE) with methanol,ethanol, or 2-propanol

Saturated pressures of three binary systems of oligomeric polyethylene glycol mono-4-nonylphenyl ether (PEGNPE) with methanol, ethanol, and 2-propanol have been measured by using an autoclave (vapour + liquid) equilibrium (VLE) apparatus at temperatures ranging from (340 to 455) K and the oligomer content ranging from 0.100 to 0.400 in mole fraction. With a given feed composition, equilibrium pressures were measured at various temperatures to obtain VLE data. The experimental data were fitted to the Antoine equation and also correlated with activity coefficient models, the NRTL and the UNIQUAC. The correlation results showed good agreement between the calculated values and the experimental data. In general, the NRTL model yielded better results. Additionally, the solvent activities were evaluated from the experimental results and were compared with those from the NRTL and the UNIQUAC models.     

Extension of the exp-6 model to the simulation of vapor-liquid equilibria of primary alcohols and their mixtures

Configurational-biased Gibbs ensemble Monte Carlo simulations were performed to obtain the phase behavior of the homologous series of primary alcohols from ethanol to 1-heptanol. Molecular interactions in these systems are modeled by a newly developed exp-6 potential in combination with a Coulombic intermolecular potential. Some of exp-6 potential parameters required to describe these alcohols were taken from the previous literature data reported for methanol and n-alkanes. The oxygen's potential parameters were optimized to fit the coexistence curve of these alcohols to the experimental data. Simulated values of saturated liquid and vapor densities, vapor pressures and critical constants of the alcohols are in good agreement with experimental data. The efficiency of the new model in the prediction of binary phase diagram of water/ethanol and n-hexane/1-propanol mixtures is also evaluated. The calculated mole fractions in the vapor and liquid phases of these binary mixtures also show satisfactory agreement with the experimental data.     

The Prediction of Surface Tension and Thermodynamic Analysis of the Surface in Mixtures of Cryogenic Liquids

The surface tensions of 42 binary cryogenic mixtures at low temperature are correlated using the Shereshefsky model and excellent results are obtained. The average percent deviation is about ～ 1.08%. The Gibbs energy change in the surface region is calculated and is used to obtain the excess number of molecular layers in the surface region. Furthermore, the model is used to derive an equation for the standard Gibbs energy of adsorption. The experimental standard Gibbs energy of adsorption is obtained from surface tension data and compared with calculated data. The agreement between experimental and calculated data is found to be very good. The magnitude of the Gibbs energy change in the surface region and the standard Gibbs energy of adsorption are discussed in terms of nature and type of intermolecular interactions in binary mixtures.     

Experimental determination and calculation of the critical curves for the binary systems of CO2 containing ketone, alkane, ester and alcohol, respectively

A set of variable-volume autoclave with a quartz window was used for the experimental determination of the high-pressure phase equilibria and critical curves. The critical temperatures, pressures, densities and mole volumes in the region near the critical point of CO₂ were examined for eleven binary systems of supercritical CO₂ (SC CO₂) with different kinds of substances (ketone, alkane, ester and alcohol), respectively. The critical curves of the above binary systems were also calculated using an equation of state. The equation consists of a hard body repulsion term and an additive perturbation term, which takes care of the attractive molecular interaction. The calculated data were compared with the experimental data, and yielded good agreements. At the same time, the values of the adjustable parameters, λ, k_σ and k_? were obtained. The critical curves of the above eleven binary systems at higher temperatures and pressures all belong to type I.     

LLE for (water + ionic liquid) binary systems using [Cxmim][BF4] (x = 6, 8) ionic liquids

Liquid–liquid equilibrium diagrams were determined for (IL + water) systems using the family of ILs 1-alkyl-3-methylimidazolium tetrafluoroborates, where the alkyl groups are hexyl and octyl ([C_xmim][BF₄] with x = 6 and 8). The gravimetric method was used to determine the equilibrium compositions at temperatures ranging from 278.15 to 340.15 K. Both systems present an upper critical solution temperature (UCST), which increases from [C₆mim][BF₄] to [C₈mim][BF₄]. The experimental data were correlated using the NRTL and eNRTL models. The binary interaction parameters were calculated for each system and model, and good agreement between experimental and calculated equilibrium compositions was obtained. Finally, the apparent Gibbs energy, enthalpy and entropy of water solution in the ILs were calculated using a modified van’t Hoff equation. The three thermodynamic functions were found to be positive for both ILs.     

Flory状态方程理论研究PS/PMMA/SAN相行为

将改进的Flory状态方程理论(EOS)引入含“分子内链段排斥性相互作用”的高分子共混物中,研究含无规共聚物的三元共混体系聚苯乙烯(PS)/聚甲基丙烯酸甲酯(PMMA)/聚苯乙烯-丙烯腈(SAN)无规共聚物的相行为,建立相应的适用于含无规共聚物三元共混体系Spinodal方程.用PS、PMMA、PAN的特征参数及其链段间相互作用参数分别计算相应共聚物的特征参数,由二元相互作用模型计算均聚物-共聚物间的相互作用能参数.在运用EOS理论研究三元均聚物共混体系相行为基础上,进一步预测PS/PMMA/SAN体系的相行为,计算并绘制不同温度下的Spinodal曲线并进行实验验证,理论计算与实验结果吻合.结果表明,EOS理论可以克服经典平均场理论的缺陷,成功描述含分子内排斥作用共混体系相行为与共聚物组成及温度之间的关系.     

Excess Enthalpy Data in some Binary Systems Containing Non-Electrolyte Solutions and their Correlations at 298.15 K - Part II

Excess enthalpy data measured at 298.15 K were collected from the literature. The data contains 48 binary systems (812 data points). The experimental data were correlated by the Redlich-Kister equation. In this research work the following thermodynamics models were also tested, Wilson, NRTL models and their parameters were calculated. A modified NRTL with composition-dependent ( f 12 ) parameter were also proposed. The correlation of excess enthalpy data in the systems using this model provides good results.     

Solubility of Fumaric Acid in Aqueous Alcohol Solutions

The solubility of fumaric acid in aqueous alcohol solutions was experimentally measured over the temperature range of (278.15–333.15) K by employing an analytical stirred-flask method. The experimental data showed that the solubility of fumaric acid in the binary mixtures increases with increases of both temperature and mass fraction of the organic solvents. The experimental data were well correlated with the modified Apelblat equation and the Buchowski–Ksiazaczak λh equation. In addition, the calculated solubilities showed good agreement with the experimental results. It was found that the modified Apelblat equation gave better correlation results than the Buchowski–Ksiazaczak λh equation. The experimental results should be useful for optimizing the process of purification of fumaric acid in industry.