水溶性高分子梯度溶液吸声机理的研究

研究了水溶性高分子涂料在其溶解过程中的吸声机理。合成了水溶性高分子涂料,并在声管中测试其溶解过程中声衰减性能。实验结果表明水溶性高分子涂料溶解过程中形成的高分子梯度溶液的声衰减效果明显优于(即大于)相应的均匀溶液。根据连续分层介质中声波传播理论建立了计算水溶性高分子溶解过程中声衰减的数学模型。计算结果与实验结果一致。由实验和理论分析结果得出了水溶性高分子涂料在其溶解过程中的梯度吸声机理,即多次反射、多次吸收,最终将声能转化为热能。     

常温高压下石膏在水中溶解及相变现象的研究

 研究常温下200~1 100 MPa压力范围内石膏的Raman光谱,原位观测了随压力升高,石膏在水中的溶解现象,其过程中伴随着石膏的相变。结果表明：压力小于407 MPa时,石膏的形态无明显变化;随着压力的升高,石膏开始溶解,溶解至一定程度,石膏发生了向半水石膏转化的相变;相变完成后,半水石膏继续溶解至消失。石膏这一溶解相变过程表明在地球内部与压力相应的深部区域内,也可能会发生矿物的溶解相变。     

电场辅助溶解法实现玻璃表面金纳米粒子的形貌控制

贵金属纳米粒子由于其非常独特的光学特性和表面活性, 在光子学、 催化和生物标识等方面都有非常重要的应用. 采用离子溅射和后续热处理相结合的方法在玻璃表面形成了尺寸大约为60-80 nm的单分散的球形金纳米粒子. 在适当的温度条件下, 采用步进式增加的强直流电场, 实现了金纳米粒子的电场辅助溶解过程. 在玻璃表面的不同颜色区域, 初始球形的金纳米粒子溶解成月蚀状形貌. 结合不同颜色区域内金纳米粒子的表面等离子体共振吸收性质和扫描电镜照片, 研究了实验条件对金纳米粒子性质的影响. 结合电场辅助溶解实验过程中的电流-电压特性, 分析了金纳米粒子在强直流电场辅助下溶解的物理过程: 金粒子中动出的电子向阳极的隧穿过程作为开始, 随后是金阳离子向玻璃基体中的传输过程和阴极提供的电子与带有正电荷的金粒子相结合的过程. 详细讨论了电场辅助溶解法实现金纳米粒子形貌控制的物理机制.     

溶液中球形晶体溶解的分析

从物质溶液浓度变化角度考虑了球形晶体在溶液中溶解随表面张力的变化,利用渐近方法求出了在溶液中球形晶体溶解的浓度和界面的近似解析解,能够计算出溶解过程中球形晶体溶解的浓度、界面演化形态.研究了表面张力对于溶液中溶质浓度分布、球晶界面形态和溶解速度的影响.结果表明,表面张力促进了球形晶体在溶液中的溶解.随着表面张力参数增大,溶液中在界面前沿的溶质浓度升高,球形晶体的溶解速度增大;随着时间的增加,溶解速度逐渐变大,球形晶体半径逐渐变小,直至溶解结束.     

多孔介质内溶解与沉淀过程的格子Boltzmann方法模拟

本文采用格子Boltzmann方法模拟了多孔介质内的溶解和沉淀现象, 并分析了雷诺数、施密特数、达姆科勒数对多孔介质孔隙结构及浓度分布的影响. 结果表明: 对于多孔介质内的溶解(沉淀)过程, 当雷诺数越大时, 孔隙率越大(小), 平均浓度值越小(大); 当达姆科勒数或施密特数较小时, 溶解和沉淀过程均受反应控制, 此时反应在多孔介质的固体表面较为均匀的发生; 当达姆科勒数或施密特数较大时, 溶解和沉淀过程均受扩散控制, 此时反应主要发生在上游及大孔隙区域.     

双颗粒在溶解条件下沉降的多相流动特性

对牛顿流体内溶解双颗粒在垂直管道中的沉降运动进行了直接数值模拟. 流体运动由守恒方程计算, 密度和黏性的变化考虑流场温度变化的影响, 通过积分粘性应力和压力获得颗粒的受力跟踪颗粒运动, 溶解引起的相变及其形状的变化由溶解潜热、溶解质量与分散相边界处的温度梯度的关系建立的方程决定. 通过颗粒和流体间相互的作用力和力矩及边界条件的施加实现相间耦合. 对双颗粒在等温流体无溶解条件和非等温流体溶解条件下的沉降过程进行了计算. 结果表明, 在一定雷诺数内, 热对流产生的颗粒尾迹处涡的脱落以及溶解引起的颗粒质量、颗粒表面形态的变化引起了颗粒的横向摆动, 并使颗粒沉降速度发生了变化.     

纯气体在均质高分子膜中吸着机理——改进的双重式吸着模型

基于双重式吸着概念,将气体在玻璃态高分子膜中的吸着过程理解为溶解和多分子层吸附两个同时发生的过程,将溶解过程理想化,并结合多分子层吸附的ＢＥＴ方程,导出了纯气体在均质高分子膜中的吸着时改进的双重式吸着模型,用文献中报导的ＰＡＮ－Ｈ２Ｏ的实验数据对模型进行了分析和验证,结果表明该模型不仅可用来解释纯气体在玻璃态高分子膜吸着时的各种现象,对纯气体在橡胶态膜中偏离亨利定律的溶解过程也能给予较好的描述。     

苯甲酸脱羧反应过程的拉曼光谱研究

应用水热金刚石压腔结合拉曼光谱技术研究了升温过程中苯甲酸在水中的变化及拉曼谱图。结果表明：低温升温过程中,苯甲酸的拉曼谱图中各个特征振动谱峰没有变化,苯甲酸没有与水反应。随着温度的继续升高,苯甲酸的拉曼谱图中的特征振动峰逐渐变弱。升至150 ℃时,羧基的拉曼特征谱峰消失,说明此过程中苯甲酸发生了脱羧反应。继续升温至170 ℃,苯甲酸溶解消失。随后将体系降至常温,发现有晶体析出。由其拉曼谱图可知,重结晶的晶体含有苯环的特征峰,说明有芳香烃析出。但是没有测到羧基的特征拉曼谱峰,说明重结晶的晶体不是苯甲酸。整个过程可以说明,芳香烃在溶解重结晶过程中是可逆的,羧基是不可逆的。     

溶解与热对流对固体颗粒运动影响的直接数值模拟

对牛顿流体内溶解与热对流对单颗粒在垂直管道中的沉降运动进行了直接数值模拟.流体运动由守恒方程计算,密度和黏性的变化考虑流场温度变化的影响,通过积分黏性应力和压力获得颗粒的受力跟踪颗粒运动,溶解引起的相变及其形状的变化由溶解潜热、溶解质量与分散相边界处的温度梯度的关系建立的方程决定.通过颗粒和流体间相互的作用力和力矩及边界条件的施加实现相间耦合.分别模拟了颗粒在等温流体、热流体、冷流体及颗粒溶解四种情况下的沉降过程.结果表明,在一定雷诺数内,热对流产生的颗粒尾迹处涡的脱落以及溶解引起的颗粒表面形态的变化引起了颗粒的横向摆动,并使颗粒沉降速度发生了变化. 关键词： 溶解 热对流 颗粒两相流 直接数值模拟     

多孔介质中含溶解反应的互溶驱替过程格子Boltzmann研究

采用格子Boltzmann方法研究了孔隙尺度下多孔介质内含流固溶解反应的互溶驱替过程,重点研究了被驱替流体与驱替流体黏性差异较大的情况下,溶解反应引起的多孔介质内部结构变化对驱替过程的影响;定量分析了不同达姆科勒数及佩克莱数下多孔介质孔隙率和驱替过程驱替效率随时间的演变.研究结果表明:达姆科勒数较大时,溶解反应的发生会在多孔介质内部生成虫洞,导致一部分被驱替流体不能被波及,驱替流体沿虫洞离开多孔介质,造成驱替效率的减少.在此基础上,随着达姆科勒数的增大,孔隙率变化越大,生成的虫洞越宽,最终驱替效率变大,但仍小于无溶解反应时的驱替效率;随着佩克莱数的增大,指进增长速度越快,孔隙率变化越小,驱替效率越小.     

六硼酸钡Ba3B6O9(OH)6热力学性质研究

本文通过水热法合成了六硼酸钡Ba3B6O9(OH)6,并通过 X射线衍射(XRD)、红外光谱(FT-IR)、综合热分析法(TG-DSC) 和扫描电子显微镜(SEM)对其进行了表征。通过微量热仪测定了Ba3B6O9(OH)6在 0.9995mol·dm-3HCl(aq) 的摩尔溶解焓为(32.34±0.58) kJ·mol-1,并计算了其标准摩尔生成焓为-(7130.664±4.2) kJ·mol-1。此外,通过基团贡献法估算了[B6O9(OH)6]6- 的摩尔生成焓为-5517.744 kJ·mol-1。     

Vapor-Liquid Equilibrium Data of Carbon Dioxide+Methyl Propionate and Carbon Dioxide+Propyl Propionate Systems

利用可变体积高压釜,在313、333、353和373 K下,测定了CO₂分别与丙烯酸甲酯和丙烯酸丙酯二元体系的气液两相平衡数据. 应用Peng-Robinson状态方程对实验数据进行计算,计算结果与实验结果具有较高的一致性. 还计算得到了不同温度和压力下CO₂在丙烯酸酯溶解过程中的Henry系数、偏摩尔焓变和偏摩尔熵变.     

Ionic association and conductance of ionic liquids in dichloromethane at temperatures from 278.15 to 303.15 K

The electrical conductances of very dilute solutions of the ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate [emim][BF₄] and 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF₄] in the low-permittivity solvent dichloromethane have been measured in the temperature range from 278.15 to 303.15 K at 5 K intervals. The data was analyzed assuming the possible presence of contact (CIP) and solvent-separated (SSIP) ion pairs in the solution on the basis of lcCM model to obtain ionic association constants, K _A, and the limiting molar conductivities, Λ_o, of these electrolytes. The examined ionic liquids are strongly associated in dichloromethane over the whole temperature range. From the temperature dependence of the limiting molar conductivities, the Eyring’s activation enthalpy of charge transport was determined. The thermodynamic functions such as Gibbs energy, entropy, and enthalpy of the process of ion pair formation were calculated from the temperature dependence of the association constants.     

Study of precipitation in NaCl:Pb2+ by light scattering and ultramicroscopy

The formation and dissolution behaviour of precipitates in NaCl : Pb²⁺ single crystals is studied by light scattering and ultramicroscopy. Measurements of Rayleigh ratio together with ultramicroscopic observations during isochronal annealing indicate the presence of two types of precipitates in as-grown crystals. Isochronal annealing after suitable thermal and thermomechanical treatments shows that precipitates of first type (I) which form and dissolve at lower temperatures, are due to homogeneous nucleation. Precipitates of the second category (II) which form and dissolve at higher temperatures are aligned along crystallographic directions and have their origin in stress-assisted processes. Isothermal annealing has been used to study the dissolution kinetics of the precipitated fraction, and it is found that the kinetics is of first order. The enthalpy of solution is determined from a study of the temperature dependence of the kinetic rate constant, in conjunction with available information on the migration energy of Pb²⁺ in NaCl. The enthalpy so deduced is in good agreement with the value as usually obtained from the concentration dependence of the dissolution temperature.     

Low-temperature heat capacities and standard molar enthalpy of formation of N-methylnorephedrine C11H17NO（s）

This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO（s） relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.     

Fusion curves and thermodynamic properties of carbon tetrachloride, chloroform, bromoform and silicon tetrachloride at pressure up to 3500 MPa

The fusion temperature as a function of pressure for carbon tetrachloride, chloroform, bromoform and silicon tetrachloride at pressures up to 3500MPa has been determined. The experimental data were fitted by the equation Tfus=T0（1 ＋ Δp/a1）^a2 exp（-a3Δp） and the changes of the maolar enthalpy and molar internal energy on fusion were calculated using the parameters of the fitted equation. Comparisons with the data from the literature show that the experimental data, parameters of fitted equations, changes of the molar enthalpy and molar internal energy are reliable.     

Low-temperature heat capacities and standard molar enthalpy of formation of pyridine-2,6-dicarboxylic acid

This paper reports that the low-temperature heat capacities of pyridine-2,6-dicarboxylic acid were measured by a precision automatic calorimeter over a temperature range from 78~K to 380~K. A polynomial equation of heat capacities as a function of temperature was fitted by the least-squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15~K were calculated and tabulated at intervals of 5~K. The constant-volume energy of combustion of the compound was determined by means of a precision rotating-bomb combustion calorimeter. The standard molar enthalpy of combustion of the compound was derived from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound was calculated from a combination of the datum of the standard molar enthalpy of combustion of the compound with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.     

Study on the Interaction Between Oxymatrine and Tungstosilicic Acid by Resonance Rayleigh Scattering and Its Analytical Applications

In the 0.1 mol · L^?1 hydrochloric acid solution, oxymatrine reacted with tungstosilicic acid to form a 2:1 ion-association complexes. This results in a great enhancement of resonance Rayleigh scattering. The maximum resonance Rayleigh scattering wavelength was located at 393 nm. Resonance Rayleigh scattering intensity was proportional to the concentration of oxymatrine in the range of 1.5–26.4 µg · mL^?1, and the detection limit (3σ) was 0.23 µg · mL^?1. The optimum conditions and the effects of coexisting substances on the reaction were investigated. The method shows a wide linear range and high sensitivity, and was applied to the determination of oxymatrine in marine capsules and human urine samples with satisfactory results. Therefore, a highly sensitive, simple, and quick method has been developed for the determination of oxymatrine.     

The electrical conductivity of chloride melts

The interrelationship between electrical conductivity, molar volume and enthalpy of mixing was studied for molten chlorides and their mixtures. The dependence of electrical conductivity and activation energy on the molar volume is different for various groups of salts. The dependence of specific conductivity on molar volume obtained for molten alkali chlorides was found to be similar to other chloride salts. The specific conductivity of binary mixtures that lack strong chemical interactions between the components can also be described by the proposed empirical equation. The enthalpy of mixing should be taken into consideration for these chemical interactions.     

Standard molar enthalpies of formation of dimethylbenzophenones

The standard (p⁰ = 0.1 MPa) molar enthalpy of formation of 3,4‐dimethylbenzophenone was derived from the standard molar energy of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was used to measure the enthalpy of sublimation of the compound. From these experimental parameters, the standard molar enthalpy of formation of 3,4‐dimethylbenzophenone, in the gaseous phase and at T = 298.15 K, was derived as ?(17.1 ± 2.9) kJ mol^?1. Density functional theory was used to investigate the gas‐phase molecular energetics of the 12 dimethylbenzophenones. Molecular geometries and vibrational frequencies were computed at the B3LYP/6‐31G(d) level of theory. The larger 6‐311+G(2d,2p) basis set was used to compute the energy of all dimethylbenzophenones and of the other compounds that were considered for the estimation of the standard molar enthalpies of formation at T = 298.15 K. The calculations show that the 2,2′‐ and 4,4′‐dimethylbenzophenones are the least and most stable isomers, respectively. Finally, the calculated enthalpy of formation of the benzophenone that was also studied experimentally, 3,4‐dimethylbenzophenone, is ?16.7 kJ mol^?1, which is in excellent agreement with the experimental result. Copyright © 2008 John Wiley & Sons, Ltd.