二氯磷酸苯酯的热力学性质

应用比重瓶法、乌氏黏度计法和静态法分别测定了二氯磷酸苯酯(PDCP)的密度、黏度和饱和蒸汽压,通过对实验数据的关联,发现密度随温度的变化适合于二次多项式,黏度随温度的变化适合于Andrade方程,饱和蒸汽压随温度的变化适合于Antoine方程,为工业化生产提供基础性数据。     

Thermodynamic properties of liquid polyethylene

Thermodynamic properties of molten polyethylene are calculated for the temperature range 100° to 300°C and for pressures up to 3000 atmospheres. The calculations are based on limited experimental data augmented by a corresponding-states correlation and an empirical equation of state. Specific volume, internal energy, enthalpy, entropy, and solubility parameter are presented as functions of temperature and pressure. The results of this study may be useful for engineering design in the high-pressure polyethylene process.     

Thermodynamic and rheological properties of rodlike polymers

Investigations on dilute and concentrated solutions of several rodlike polymers are described. The former includes absolute and intensity fluctuation light scattering, exclusion chromatography and viscometry. The latter includes rheological properties of isotropic and anisotropic solutions. The discussion includes data for four rodlike polymers, each soluble only in strong sulphonic acids. The role of electrostic interactions and molecular association on the properties measured is considered. The similarities and differences of the rheological behaviour with that typically found with flexible chain polymers are pointed out.     

环戊酮-甲醇氢键复合物的热力学性质

测定了常压下环戊酮(CPN)与CH3OH二元混合体系在283.15—333.15 K之间全摩尔分数范围的密度,并基于密度数据计算了该混合体系的超额摩尔体积。其超额摩尔体积在所测定的温度和全摩尔分数范围内均呈负偏差。表明该二元混合体系中分子间的交叉缔合作用强于分子间的自缔合作用。同时采用B3LYP/6-311++G(d,p)方法研究了CPN与CH3OH氢键复合物的氢键结构和性质。经几何优化和振动分析获得了2种稳定的氢键复合物。基于统计热力学方法计算了200.00—800.00 K之间从单体形成氢键复合物的热力学性质变化,结果表明CPN和CH3OH分子间氢键交叉缔合是一个放热、熵减的热力学非自发过程。     

非氧化物复合耐火材料的热力学性能

为了在耐火材料中能动地应用非氧化物,系统了解非氧化物的热力学性质是非常必要的。为此,首分析了非氧化物在氧化气氛下的不稳定性及顺序,并就如何转变这个不利的性质,以实现在氧化气氛下烧结非氧化物复合材料而提出了“逆反应烧结”工艺。在深入研究Si、Al系氮化物的氧化机理后发现,当氧分压低于“转换氧分压”时,可显著生成其气态的亚氧化物。亚氧化物可以在邻近表面层沉积,形成致密层。致密层的形成使材料具有“自阻碍氧化”的性能。Si、Al的加入可增加亚氧化物的含量,从而加厚、加宽致密层,使材料的抗氧化和抗侵蚀能力得到提高。文中详述了Si3N4 -Al2O3、Si3N4 -MgO和Si3N4 -SiC三个体系的研究情况。结果表明:逆反应烧结工艺可制备出性能良好的复合物;Si、Al除可促进烧结外,还能提高致密层的密度和宽度。     

Solution properties of lignin. Thermodynamic properties and molecular weight determinations

Number-average molecular weights and the thermodynamic parameters ΔF?₁, ΔH?₁, and ΔS?₁ have been obtained for lignin in the solvents dimethylsulfoxide, dimethyl-formamide, and dioxane. Widely different molecular weights were found in the different solvents and at the different temperatures as a consequences of molecular association. Analysis of the thermodynamic parameters revealed that these quantities are dominated by the change in solvent structure accompanying the solution process. A correlation between the “goodness” of a lignin solvent and the Hildebrand solubility parameter is consequently misleading in such systems.     

Sensory properties of vanadium pentoxide films in gaseous media

Vanadium pentoxide films are synthesized by pyrolysis. The optimum conditions of heat treatment providing for the effective use of films as gas sensors are determined. The sensitivity of the films to different gaseous media (vapors of ethanol, methanol, and argon) is investigated by measuring the electrical conductivity in the temperature range 300–800 K.     

溶析结晶法提纯龙脑的热力学研究

采用激光合成法测定了龙脑在不同比例乙醇水溶液中的溶解度,并分别采用多项式经验模型、modified Apelblat模型对溶解度数据进行拟合,拟合系数R~2均在0.999 0以上,总平均相对偏差均小于1%,取得了较好的关联效果,建立了理想的溶解度模型。在此基础上,计算了龙脑在乙醇/水混合溶剂中溶解的热力学函数,讨论了焓熵补偿现象,证明龙脑的溶解过程为非自发熵驱动的吸热过程,且焓变对吉布斯自由能变的贡献最大。在不同的工艺条件下测定了龙脑在乙醇水溶液中结晶的介稳区宽度,得出乙醇/水体系溶析结晶的工艺参数:结晶温度15—25℃,搅拌转速不大于150 r/min,溶剂比w(水/乙醇)控制在0.5以内。这些工艺参数为乙醇/水溶析结晶工艺的优化奠定了理论基础。     

Thermodynamic properties of the uninegative hydroxyl ion

An assessment is made of thermodynamic properties of the uninegative hydroxyl ion OH^? (g). Special attention is given to the evaluation of individual thermodynamic functions for hydration of the ion. Entropy data are considered in relation to the hydroxide ion in aqueous solution acting as a “structure maker”. Values for the lattice potential energies of alkali metal hydroxides are given.     

Thermodynamic sorption properties of potato and sweet potato flakes

The moisture sorption isotherms of potato and sweet potato flakes were determined using a gravimetric method at 15, 20, 25 and 30 °C for water activity ranging from 0.1 to 0.9. The GAB was found to be the most suitable for describing the relationship between equilibrium moisture content and water activity for the whole range of temperatures and relative humidities. The differential and integral thermodynamic functions of enthalpy and entropy were estimated from the sorption data for potato and sweet potato flakes. The differential enthalpy was determined using the Clausius–Clapeyron equation and decreased with increase in moisture content, the same behavior as found for differential entropy. From the values obtained for differential enthalpy and entropy, it was verified that the compensation theory could be applied, the process being carried out by enthalpy (T_β > T_hm) and non-spontaneous (ΔG > 0). The spreading pressures increased with increasing water activity for all the temperatures studied. With respect to the integral properties, it was observed that the enthalpy increased with moisture content, but the entropy decreased. It was also shown that for the moisture range evaluated, the values for integral entropy were negative.     

油页岩催化热解气态产物析出特性

采用气相色谱仪和微量硫分析仪在铝甑干馏炉上考察了不同催化剂作用下油页岩热解干馏气和含硫化合物的析出特点。结果表明:催化热解降低了干馏气的产率,不同催化剂对干馏气组成的影响不同;Ni2O3和环烷酸钴促进氢气的析出,降低了CH4的析出;13X分子筛促进烃类析出,Ni2O3和活性白土降低了烃类的析出。催化剂促进了CO2的析出,但对CO析出的影响较小。与常规热解相比,催化热解促进了油页岩干馏气中含硫化合物的析出,皂土和Mo S2的促进作用最大,总硫析出量比常规热解提高4.58倍和3.95倍;活性白土和环烷酸钴的促进作用较常规热解提高了64.01%和32.95%。     

Thermodynamic properties of poly(butylene terephthalate)

Specific heat of poly(butylene terephthalate) was measured in a Mettler TC 10 differential thermal analyzer. Its glass transition, melting behaviour, as well as its enthalpy, entropy, Gibbs free energy, and the rigidity of the chains are described.     

Thermodynamic properties of DyNi intermetallic compounds

Electromotive force (EMF) measurements for various DyNi intermetallic compounds in two-phase coexisting states were carried out in the temperature range of 673-773 K in a molten LiCl-KCl-DyCl₃ (0.5 mol%) system. The activities and relative partial molar Gibbs free energies of Dy were obtained from the measured EMFs for various DyNi intermetallic compounds, DyNi₂, DyNi₃, Dy₂Ni₇, and DyNi₅. The relative partial molar entropies and enthalpies of Dy were also calculated from the temperature dependence of the EMFs. The activities and relative partial molar properties of Ni in the compounds were calculated from the activities of Dy by using Gibbs-Duhem equation. Finally, the standard Gibbs free energies of formation for the DyNi intermetallic compounds were estimated.     

Thermodynamic properties of normal butane at refrigeration temperatures

Presented in both English and SI units are tables of the thermodynamic properties of normal butane over the temperature range -22 to +122°F (-30 to +50°C). Values are tabulated of the volume, enthalpy, and entropy for the subcooled liquid, the saturated liquid and vapor and the superheated vapor in both unit systems. The data used to calculate these properties have been carefully evaluated and include very recent values of the low temperature heat capacity of the vapor. Two enthalpy-entropy charts (Mollier diagrams), one in each of the unit systems are presented. These are suitable for the design of machinery used in thermo-mechanical energy cycles such as the freezing and eutectic processes for treating sea water and waste water. The calculated thermodynamic properties are the only ones available for n-butane which cover the above complete temperature range.     

Thermodynamic and physical properties of crystals formed from dilute solutions

Some of the thermodynamic and physical properties of crystals of linear polyethylene, formed from dilute solution are discussed. These properties include density, enthalpy of fusion, infrared absorption spectrum, selective oxidation and dynamic mechanical measurements. Despite the fact that electron microscopic examination reveals an apparent geometric regularity to these crystals, all these physical measurements yield a consistent interpretation in that they require about 15–20% of the chain units to be in a non-random conformation, and to form a disordered amorphous overlayer. Detailed studies of the experimentally observed relations between the crystallite thickness, crystallization temperature, and dissolution temperature (melting temperature in a dilute solution) are also presented. A thermodynamic analysis of the dissolution temperature-size relations, based on independently determined equilibrium solubility temperatures, indicates that the interfacial free-energy characteristic of the mature crystallites is significantly different from that involved in nucleation. The interfacial structures of the nucleus and the crystallites must, therefore, also be different. Size control by a nucleation process can be demonstrated from very general theoretical considerations. However, the detailed molecular structure characteristic of the nucleus cannot be specified solely from the fact that this process is size controlling.     

Thermodynamic interactions and nonlinear rheological properties of plasticized polyvinyl chloride

The nature of thermodynamic interactions in plasticized semicrystalline materials has a profound effect on the rheological properties. In this work we investigated the effect of mixing thermodynamics on the linear and nonlinear rheological properties of plasticized poly(vinyl chloride). The stress-dependent creep compliance has been modeled in terms of stress, temperature, concentration, and thermodynamic interaction strength.     

The influence of gaseous chlorine on the chemical and catalytic properties of alumina

The influence of gaseous chlorine on the chemical and catalytic properties of alumina was investigated. Cl₂ reacts both with surface OH groups and with surface oxygen anions possessing electron-donating power, forming new surface sites. When such chlorine treatment is performed at a low temperature (293 K), both Lewis and Bronsted acid centres are formed. High temperature chlorination leads exclusively to Lewis acid sites. It is proposed that such Lewis sites are responsible for olefin isomerization reactions.