Isotope quantum effects in water around the freezing point

We have measured the difference in electronic structure factors between liquid H(2)O and D(2)O at temperatures of 268 and 273 K with high energy x-ray diffraction. These are compared to our previously published data measured from 279 to 318 K. We find that the total structural isotope effect increases by a factor of 3.5 over the entire range, as the temperature is decreased. Structural isochoric temperature differential and isothermal density differential functions have been used to compare these data to a thermodynamic model based upon a simple offset in the state function. The model works well in describing the magnitude of the structural differences above approximately 310 K, but fails at lower temperatures. The experimental results are discussed in light of several quantum molecular dynamics simulations and are in good qualitative agreement with recent temperature dependent, rotationally quantized rigid molecule simulations.     

Effect of precursor calcination temperature on the microstructure and thermoelectric properties of Ca3Co4O9 ceramics

Ca₃Co₄O₉ (CCO) powder precursors were prepared by the chemical sol–gel route and calcined at various temperatures between 923?K (CCO-923?K) and 1,073?K (CCO-1,073?K). The calcination temperature was found to be a critical factor affecting the microstructure and thermoelectric properties of CCO ceramic bulk samples. The grain size increases with calcination temperature. The nano-crystals with size about 100?nm in the powders calcined at 923?K promote large crystal growth and texture development during sintering. Bulk pellets made from CCO-923?K powder have large crystal grains, uniform grain size distribution, and a high degree of crystal alignment. By contrast, pellets made from CCO powders at higher calcination temperatures have a bimodal distribution of large and small grains and a large amount of randomly oriented grains. Transmission electron microscopy analysis shows that each crystal grain (identified in SEM images) consists of bundles of CCO nano-lamellas. The nano-lamellas within one bundle share the same c-axis orientation and have fiber texture. The electrical resistivity of CCO-923?K is weakly dependent on operating temperature. Compared to the CCO-1,073?K sample, the CCO-923?K sample has the highest power factor, a lower thermal conductivity, and higher electrical conductivity.     

Magnetic properties of dilute magnetic semiconductor Cd<Subscript>0.82</Subscript>Mn<Subscript>0.18</Subscript>GeAs<Subscript>2</Subscript> under high pressures

We have studied the effect of high pressures on the electrical and magnetic properties of dilute magnetic semiconductor Cd_0.82Mn_0.18GeAs₂. Electrical resistivity, Hall coefficient, transverse and longitudinal magnetic resistance, and magnetic susceptibility have been measured under high pressures (up to 9 GPa). The energy of a manganese impurity level was estimated at 155 meV from electrical resistivity and Hall factor versus temperature curves at the atmospheric pressure. Structural and magnetic phase transitions have been discovered in Hall resistance versus magnetic field curves measured at various temperatures; abnormal and normal Hall factors have been calculated.     

The electrical resistivity of USix(1.8 ⩽ x ⩽ 2.0)

Two specimens of USi_x(x ≲ 2) were arc-melted and their resistivity was measured from 2 K to 250 K. X-ray data show that both specimens have the body-centred tetragonal structure expected for USi_1.88 and magnetization measurements below 4K confirm that there is no superconductivity or magnetic ordering above 1.5 K. The temperature variation of the resistivity is discussed in terms of coherence developing at low temperatures in strongly hybridized f-conduction electron states.     

Ternary liquid–liquid equilibria for mixtures of (ethanol + toluene + n -decane)

The data on the liquid–liquid equilibrium in (ethanol?+?toluene?+?n-decane) have been measured at three temperatures 298.15, 303.15 and 313.15?K and ambient pressure. Gas liquid chromatography has been employed, to determine the composition of the substances in liquid phases. The measured tie-line data are presented. The experimental ternary liquid–liquid equilibrium data have been correlated, using the universal quasi chemical (UNIQUAC) and non-random tow-liquid (NRTL) activity coefficient models to obtain the binary interaction parameters of these components. Both the UNIQUAC and NRTL models, satisfactorily predict the equilibrium compositions. The partition coefficients and the selectivity factor of the toluene extraction from n-decane mixtures were calculated and presented.     

Isobaric vapour–liquid phase diagram and excess properties for the binary system 1,4-dioxane + water at 298.15 K, 318.15 K and 338.15 K

Isobaric vapour–liquid equilibrium (VLE) data have been measured for the binary system (1,4-dioxane + water) at atmospheric pressure. The compositions of the two phases in equilibrium were taken from the refractive indices curve of the system. The equilibrium data show a positive deviation from ideality and reveal an azeotrope. VLE data have been used to calculate the activity coefficients of the two components at 298.15 K, 318.15 K and 338.15 K. The excess properties have been deduced at these temperatures. Molar Gibbs free energy at liquid state was expressed as a function of composition and temperature. At the liquid state, excess entropies of the present system are negative over the entire composition range. Molecular-scale segregation in this system was proved.     

2H NMR和DSC法研究十二烷基磺酸钠-正戊醇-水三元体系的溶致液晶

测定了十二烷基磺酸钠/正戊醇/水体系的相平衡,在相图中的液晶区选取样品点,采用²H NMR和差示扫描量热方法,并结合其液晶纹理,研究了该体系液晶相的结构特点。结果表明,在一定温度下,整个液晶区均为层状液晶,其相结构不随水含量和醇含量的变化而变化。在组成固定的情况下,该体系液晶的相结构随温度的升高而发生变化。     

The abnormal changes of electrical resistivity in liquid Pb–In alloys

Electrical resistivity of liquid lead and indium (Pb–In) alloys with different compositions has been measured using the four-probe method in a large temperature range. Marked turning points on each resistivity–temperature (ρ–T) curve of the liquid Pb–In alloys can be observed far above the liquidus. The unusual variation of the resistivity of Pb–In melts suggests a structural transition of these melts, for resistivity is a sensitive parameter to the structure. Moreover, the DSC experiment of Pb–In melts supports the existence of a liquid–liquid (L–L) structure transition in Pb–In melts. Such a L–L structural transition can be described in terms of the gradual disappearance of atomic bonds corresponding to the crystal structure and/or to a reduction of the size of pre-formed atomic clusters. This implies an increase of disorder in the high temperature melts. The transition temperatures depend on the composition of Pb–In melts and the onset transition temperatures of the intermediate phase (α) Pb–63%In and Pb–70.6%In melts are higher than that of other compositions.     

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。     

High temperatures and high pressures Brillouin scattering studies of liquid H(2)O+CO(2) mixtures

The Brillouin scattering spectroscopy studies have been conducted in a diamond anvil cell for a liquid mixtures composed of 95 mol?% H(2)O and 5 mol?% CO(2) under high temperatures and pressures. The sound velocity, refractive index, density, and adiabatic bulk modulus of the H(2)O+CO(2) mixtures were determined under pressures up to the freezing point at 293, 453, and 575 K. It is found from the experiment that sound velocities of the liquid mixture are substantially lower than those of pure water at 575 K, but not at lower temperatures. We presented an empirical relation of the density in terms of pressure and temperature. Our results show that liquid H(2)O+CO(2) mixtures are more compressible than water obtained from an existing equation of state of at 453 and 575 K.     

The thermal conductivity of alumina nanoparticles dispersed in ethylene glycol

The thermal conductivities of several nanofluids (dispersions of alumina nanoparticles in ethylene glycol) were measured at temperatures ranging from 298 to 411 K using a liquid metal transient hot wire apparatus. Our measurements span the widest range of temperatures that have been investigated to date for any nanofluid. A maximum in the thermal conductivity versus temperature behavior was observed at all mass fractions of nanoparticles, closely following the behavior of the base fluid (ethylene glycol). Our results confirm that additional temperature contributions inherent in Brownian motion models are not necessary to describe the temperature dependence of the thermal conductivity of nanofluids. Our results also show that the effect of mass or volume fraction of nanoparticles on the thermal conductivity of nanofluids can be correlated using the Hamilton and Crosser or Yu and Choi models with one adjustable parameter (the shape factor in the Hamilton and Crosser model, or the ordered liquid layer thickness in the Yu and Choi model).     

Volumetric and speed-of-sound measurements for liquid tetrachloromethane under pressure

For liquid tetrachloromethane (p, V_m, T) has been measured with a direct-weighing apparatus from 329 to 409 K and at pressures to 55 MPa. The results compare very well with published values, especially at the lower temperatures, and have been fitted to a modified form of the Tait equation. Speeds of sound c have been measured at temperatures between 283 and 455 K and pressures to 125 MPa. Experiments have been carried out at 3 MHz with a newly constructed apparatus, using a pulse-echo overlap technique.     

Essential oil deterpenation by solvent extraction using 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate ionic liquid

Taking into account that heat application can have undesirable effects in essential oil properties, liquid extraction comes up as a promising process instead of distillation for citrus oil deterpenation. In this work the suitability of using the ionic liquid 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate as a solvent for the extraction of linalool from citrus essential oil (which has been simulated as a mixture of limonene and linalool) has been analyzed. Liquid–liquid equilibrium data at three different temperatures (298.15 K, 308.15 K and 318.15 K) have been reported and successfully correlated using NRTL model. The best results were achieved using α = 0.1 for the systems at 298.15 K and 308.15 K and α = 0.2 at 318.15 K. The solute distribution ratio has showed values close to one and high values of selectivity have been achieved.     

Experimental determination of the NH4NO3/(NH4)2SO4/H2O phase diagram

We have studied the thermodynamic properties of the ammonium nitrate/ammonium sulfate/water system using differential scanning calorimetry and infrared spectroscopy of thin films at low temperatures. This is the first study focused on low temperatures, as previous experimental work on this system has been at 273 K and above. We have combined our experimental results with melting point data from the literature at high temperatures to create a solid/liquid phase diagram of the ammonium nitrate/ammonium sulfate/water system for temperatures below 343 K. Using phase diagram theory and Alkemade lines, we predict which solids are stable at equilibrium for all concentrations within the studied region. We also observed the decomposition of a solid at low temperatures which has not previously been reported. Finally, we have compared our predicted solids and final melting temperatures to the Aerosol Inorganics Model (AIM).     

Investigation of energy and structural changes of Lin (n=3, 4) microclusters based on temperature

The energy and structural changes of lithium microclusters based on temperature has been investigated by using Molecular-Dynamic simulation Method. Two and three-body interacted semi-empiric potential energy formula that characterized the interaction has been used. It has been calculated that the dissociation of atoms from cluster has started after 1300 K for Li₃ and 1350 K for Li₄, respectively. Dissociations at the fixed temperatures are very close to the expected values of the lithium metal. Additionally, it has been observed that Li₄ microclusters above 1000 K and Li₃ clusters above 700 K temperatures have steady structures in two different energy values.     

Thermodynamic properties of organic oxygen compounds 42. Physical and thermodynamic properties of benzaldehyde

The following properties of a purified sample of benzaldehyde have been measured: vapour pressure (311 to 481 K); density of liquid (293 to 490 K); heat capacity of crystals and liquid (13 to 425 K); enthalpy of fusion; triple-point, normal boiling, and critical temperatures; and enthalpy of combustion in oxygen. From the measurements, the enthalpy of vaporization, the entropy (crystal, liquid, and ideal gas); and the enthalpy of formation (liquid and ideal gas) have been calculated. Thermodynamic functions (0 to 1000 K) of the ideal gas have been calculated from a vibrational assignment and molecular dimensions.     

在i-PrOH-H2O混合溶剂中硫酸镁离子对缔合热力学研究

50年代,Nair等利用电动势法研究了硫酸镁离子对缔合过程的热力学量,Chand等也对水溶液中硫酸镁离子对的性质做过研究,宋彭生和孙柏对硼酸镁和硼酸钙离子对做了研究,目前,还没有人研究有机溶剂对[MgSO4]^0离子对标准缔合常数Kb的影响,本文在278.15-318.15K温度范围内,测定了无液接电池（A）,（B）的电动热E：Pt,H2(101.325kPa)|(HCl(m1),H2SO4(m2),i-PrOH(x),H2O(1-x)|AgCl-Ag(A) Pt,H2(101.325kPa)|(HCl(m1),MgSO4(m2),i-PrOH(x),H2O(1-x)|AgCl-Ag(B)其中,mi为物质i的质量摩尔浓度,x表示异丙醇i-PrOH在混合溶剂中的摩尔分数,保持x=0.05。利用电池A的电动势,在Debye-Hueckel理论基础上,确定了H2SO4在混合溶剂中的二级标准解离常数K2;利用电池B的电动势,确定了[MgSO4]^0离子在对沸合溶剂中的标准缔合常数KD,根据实验结果计算了离子缔合熵和焓,讨论了异丙醇对KD的影响,指出离子缔合熵是形成离子对的推动力。     

On the variation of the structure of liquid deuterium fluoride with temperature

The structure of liquid deuterium fluoride has been measured using pulsed neutron diffraction and high energy x-ray diffraction techniques as a function of temperature. The neutron experiments were performed at T=296+/-2 K, 246+/-2 K, and 193+/-2 K and the x-ray measurements carried out at 296+/-2 K and 195+/-2 K. The x-ray pair correlation functions, which are dominated by fluorine-fluorine interactions, show the first peak at approximately 2.53+/-0.05 A remains very nearly invariant with decreasing temperature. Peaks around 4.5 and 5.0 A also appear at both temperatures in the x-ray data. In contrast, the intermolecular peaks in the total neutron pair correlation function show that significant systematic local structural changes occur as the temperature is lowered. The first intermolecular peak position shortens from 1.64+/-0.05 A at 296 K to 1.56+/-0.05 A at 195 K. Although there are overlapping contributions from the intermolecular hydrogen-fluorine and hydrogen-hydrogen correlations, it is clear that the temperature dependent structural changes are largely due to a rearrangement of the deuterium atom positions in the fluid. By comparison with partial structure factor data the hydrogen bonds appear to become more linear at lower temperatures.     

New synthesis route to and physical properties of lanthanum monoiodide

A fast procedure to produce LaI by reduction of LaI2 or LaI3 in a Na melt under argon at 550 degrees C is given. The structural studies performed by means of powder X-ray diffraction as well as transmission electron microscopy are consistent with previous single-crystal results. Measurements of the electrical resistance on polycrystalline samples reveal metallic behavior for LaI in the range 10-300 K. Upon cooling, a small maximum in the resistivity has been observed at 67 K. This anomaly disappears upon heating a sample, however, yielding a hysteresis in rho(T) above 70 K. From the Pauli susceptibility, an electron density of states at the Fermi level of about 0.3 eV(-1).formula unit(-1) has been estimated, as compared with a value of 1.0 eV(-1).formula unit(-1) derived from ab initio LMTO band structure calculations.     

The structure factor for liquid lead

Abstract

The structure factor for liquid lead at the temperatures 613 K, 643 K, 863 K and 1163 K are measured by neutron diffraction. Extensive comparisons to earlier measurements are made as well as comparisons to different hard-core models.